ath11k: Fix frames flush failure caused by deadlock

In the Linux kernel, the following vulnerability has been resolved:

ath11k: Fix frames flush failure caused by deadlock

We are seeing below warnings:

kernel: [25393.301506] ath11k_pci 0000:01:00.0: failed to flush mgmt transmit queue 0
kernel: [25398.421509] ath11k_pci 0000:01:00.0: failed to flush mgmt transmit queue 0
kernel: [25398.421831] ath11k_pci 0000:01:00.0: dropping mgmt frame for vdev 0, is_started 0

this means ath11k fails to flush mgmt. frames because wmi_mgmt_tx_work
has no chance to run in 5 seconds.

By setting /proc/sys/kernel/hung_task_timeout_secs to 20 and increasing
ATH11K_FLUSH_TIMEOUT to 50 we get below warnings:

kernel: [ 120.763160] INFO: task wpa_supplicant:924 blocked for more than 20 seconds.
kernel: [ 120.763169] Not tainted 5.10.90 #12
kernel: [ 120.763177] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kernel: [ 120.763186] task:wpa_supplicant state:D stack: 0 pid: 924 ppid: 1 flags:0x000043a0
kernel: [ 120.763201] Call Trace:
kernel: [ 120.763214] __schedule+0x785/0x12fa
kernel: [ 120.763224] ? lockdep_hardirqs_on_prepare+0xe2/0x1bb
kernel: [ 120.763242] schedule+0x7e/0xa1
kernel: [ 120.763253] schedule_timeout+0x98/0xfe
kernel: [ 120.763266] ? run_local_timers+0x4a/0x4a
kernel: [ 120.763291] ath11k_mac_flush_tx_complete+0x197/0x2b1 [ath11k 13c3a9bf37790f4ac8103b3decf7ab4008ac314a]
kernel: [ 120.763306] ? init_wait_entry+0x2e/0x2e
kernel: [ 120.763343] __ieee80211_flush_queues+0x167/0x21f [mac80211 335da900954f1c5ea7f1613d92088ce83342042c]
kernel: [ 120.763378] __ieee80211_recalc_idle+0x105/0x125 [mac80211 335da900954f1c5ea7f1613d92088ce83342042c]
kernel: [ 120.763411] ieee80211_recalc_idle+0x14/0x27 [mac80211 335da900954f1c5ea7f1613d92088ce83342042c]
kernel: [ 120.763441] ieee80211_free_chanctx+0x77/0xa2 [mac80211 335da900954f1c5ea7f1613d92088ce83342042c]
kernel: [ 120.763473] __ieee80211_vif_release_channel+0x100/0x131 [mac80211 335da900954f1c5ea7f1613d92088ce83342042c]
kernel: [ 120.763540] ieee80211_vif_release_channel+0x66/0x81 [mac80211 335da900954f1c5ea7f1613d92088ce83342042c]
kernel: [ 120.763572] ieee80211_destroy_auth_data+0xa3/0xe6 [mac80211 335da900954f1c5ea7f1613d92088ce83342042c]
kernel: [ 120.763612] ieee80211_mgd_deauth+0x178/0x29b [mac80211 335da900954f1c5ea7f1613d92088ce83342042c]
kernel: [ 120.763654] cfg80211_mlme_deauth+0x1a8/0x22c [cfg80211 8945aa5bc2af5f6972336665d8ad6f9c191ad5be]
kernel: [ 120.763697] nl80211_deauthenticate+0xfa/0x123 [cfg80211 8945aa5bc2af5f6972336665d8ad6f9c191ad5be]
kernel: [ 120.763715] genl_rcv_msg+0x392/0x3c2
kernel: [ 120.763750] ? nl80211_associate+0x432/0x432 [cfg80211 8945aa5bc2af5f6972336665d8ad6f9c191ad5be]
kernel: [ 120.763782] ? nl80211_associate+0x432/0x432 [cfg80211 8945aa5bc2af5f6972336665d8ad6f9c191ad5be]
kernel: [ 120.763802] ? genl_rcv+0x36/0x36
kernel: [ 120.763814] netlink_rcv_skb+0x89/0xf7
kernel: [ 120.763829] genl_rcv+0x28/0x36
kernel: [ 120.763840] netlink_unicast+0x179/0x24b
kernel: [ 120.763854] netlink_sendmsg+0x393/0x401
kernel: [ 120.763872] sock_sendmsg+0x72/0x76
kernel: [ 120.763886] ____sys_sendmsg+0x170/0x1e6
kernel: [ 120.763897] ? copy_msghdr_from_user+0x7a/0xa2
kernel: [ 120.763914] ___sys_sendmsg+0x95/0xd1
kernel: [ 120.763940] __sys_sendmsg+0x85/0xbf
kernel: [ 120.763956] do_syscall_64+0x43/0x55
kernel: [ 120.763966] entry_SYSCALL_64_after_hwframe+0x44/0xa9
kernel: [ 120.763977] RIP: 0033:0x79089f3fcc83
kernel: [ 120.763986] RSP: 002b:00007ffe604f0508 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
kernel: [ 120.763997] RAX: ffffffffffffffda RBX: 000059b40e987690 RCX: 000079089f3fcc83
kernel: [ 120.764006] RDX: 0000000000000000 RSI: 00007ffe604f0558 RDI: 0000000000000009
kernel: [ 120.764014] RBP: 00007ffe604f0540 R08: 0000000000000004 R09: 0000000000400000
kernel: [ 120.764023] R10: 00007ffe604f0638 R11: 0000000000000246 R12: 000059b40ea04980
kernel: [ 120.764032] R13: 00007ffe604
---truncated---