wifi: ath11k: Ignore frags from uninitialized peer in dp.

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

wifi: ath11k: Ignore frags from uninitialized peer in dp.

When max virtual ap interfaces are configured in all the bands with
ACS and hostapd restart is done every 60s, a crash is observed at
random times.
In this certain scenario, a fragmented packet is received for
self peer, for which rx_tid and rx_frags are not initialized in
datapath. While handling this fragment, crash is observed as the
rx_frag list is uninitialised and when we walk in
ath11k_dp_rx_h_sort_frags, skb null leads to exception.

To address this, before processing received fragments we check
dp_setup_done flag is set to ensure that peer has completed its
dp peer setup for fragment queue, else ignore processing the
fragments.

Call trace:
ath11k_dp_process_rx_err+0x550/0x1084 [ath11k]
ath11k_dp_service_srng+0x70/0x370 [ath11k]
0xffffffc009693a04
__napi_poll+0x30/0xa4
net_rx_action+0x118/0x270
__do_softirq+0x10c/0x244
irq_exit+0x64/0xb4
__handle_domain_irq+0x88/0xac
gic_handle_irq+0x74/0xbc
el1_irq+0xf0/0x1c0
arch_cpu_idle+0x10/0x18
do_idle+0x104/0x248
cpu_startup_entry+0x20/0x64
rest_init+0xd0/0xdc
arch_call_rest_init+0xc/0x14
start_kernel+0x480/0x4b8
Code: f9400281 f94066a2 91405021 b94a0023 (f9406401)

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.7.0.1-01744-QCAHKSWPL_SILICONZ-1