wifi: ath11k: Add missing hw_ops->get_ring_selector() for IPQ5018

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

wifi: ath11k: Add missing hw_ops->get_ring_selector() for IPQ5018

During sending data after clients connected, hw_ops->get_ring_selector()
will be called. But for IPQ5018, this member isn't set, and the
following NULL pointer exception will be occurred:

[ 38.840478] 8<--- cut here ---
[ 38.840517] Unable to handle kernel NULL pointer dereference at virtual address 00000000
...
[ 38.923161] PC is at 0x0
[ 38.927930] LR is at ath11k_dp_tx+0x70/0x730 [ath11k]
...
[ 39.063264] Process hostapd (pid: 1034, stack limit = 0x801ceb3d)
[ 39.068994] Stack: (0x856a9a68 to 0x856aa000)
...
[ 39.438467] [<7f323804>] (ath11k_dp_tx [ath11k]) from [<7f314e6c>] (ath11k_mac_op_tx+0x80/0x190 [ath11k])
[ 39.446607] [<7f314e6c>] (ath11k_mac_op_tx [ath11k]) from [<7f17dbe0>] (ieee80211_handle_wake_tx_queue+0x7c/0xc0 [mac80211])
[ 39.456162] [<7f17dbe0>] (ieee80211_handle_wake_tx_queue [mac80211]) from [<7f174450>] (ieee80211_probereq_get+0x584/0x704 [mac80211])
[ 39.467443] [<7f174450>] (ieee80211_probereq_get [mac80211]) from [<7f178c40>] (ieee80211_tx_prepare_skb+0x1f8/0x248 [mac80211])
[ 39.479334] [<7f178c40>] (ieee80211_tx_prepare_skb [mac80211]) from [<7f179e28>] (__ieee80211_subif_start_xmit+0x32c/0x3d4 [mac80211])
[ 39.491053] [<7f179e28>] (__ieee80211_subif_start_xmit [mac80211]) from [<7f17af08>] (ieee80211_tx_control_port+0x19c/0x288 [mac80211])
[ 39.502946] [<7f17af08>] (ieee80211_tx_control_port [mac80211]) from [<7f0fc704>] (nl80211_tx_control_port+0x174/0x1d4 [cfg80211])
[ 39.515017] [<7f0fc704>] (nl80211_tx_control_port [cfg80211]) from [<808ceac4>] (genl_rcv_msg+0x154/0x340)
[ 39.526814] [<808ceac4>] (genl_rcv_msg) from [<808cdb74>] (netlink_rcv_skb+0xb8/0x11c)
[ 39.536446] [<808cdb74>] (netlink_rcv_skb) from [<808ce1d0>] (genl_rcv+0x28/0x34)
[ 39.544344] [<808ce1d0>] (genl_rcv) from [<808cd234>] (netlink_unicast+0x174/0x274)
[ 39.551895] [<808cd234>] (netlink_unicast) from [<808cd510>] (netlink_sendmsg+0x1dc/0x440)
[ 39.559362] [<808cd510>] (netlink_sendmsg) from [<808596e0>] (____sys_sendmsg+0x1a8/0x1fc)
[ 39.567697] [<808596e0>] (____sys_sendmsg) from [<8085b1a8>] (___sys_sendmsg+0xa4/0xdc)
[ 39.575941] [<8085b1a8>] (___sys_sendmsg) from [<8085b310>] (sys_sendmsg+0x44/0x74)
[ 39.583841] [<8085b310>] (sys_sendmsg) from [<80300060>] (ret_fast_syscall+0x0/0x40)
...
[ 39.620734] Code: bad PC value
[ 39.625869] ---[ end trace 8aef983ad3cbc032 ]---