rx_desc_get_ldpc_support is missing in wcn6855_ops, resulting on WCN6855 a
kernel crash after connecting to an AP and waiting for few minutes. Fix it by
implementing WCN6855's version of this field and adding it to wcn6855_ops.

Crash stack:
[  184.862605] BUG: kernel NULL pointer dereference, address: 0000000000000000
[  184.862615] #PF: supervisor instruction fetch in kernel mode
[  184.862620] #PF: error_code(0x0010) - not-present page
[  184.862626] PGD 0 P4D 0
[  184.862634] Oops: 0010 [#1] PREEMPT SMP PTI
[  184.862642] CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Not tainted 5.16.0-wt-ath+ #1
[  184.862651] Hardware name: Intel(R) Client Systems NUC8i7HVK/NUC8i7HVB, BIOS HNKBLi70.86A.0059.2019.1112.1124 11/12/2019
[  184.862656] RIP: 0010:0x0
[  184.862669] Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
[  184.862673] RSP: 0018:ffff9eedc003cca8 EFLAGS: 00010202
[  184.862680] RAX: 0000000000000000 RBX: ffff9eedc003cd30 RCX: 0000000000000002
[  184.862686] RDX: 0000000000000002 RSI: ffffffffc1773458 RDI: ffff8eb5843de240
[  184.862692] RBP: ffff8eb59685a0e0 R08: 0000000000000001 R09: ffff8eb6fef2b000
[  184.862700] R10: ffff9eedc003cd70 R11: ffff8eb5880a9ff0 R12: ffff8eb5843de240
[  184.862707] R13: 0000000000000000 R14: 0000000000000008 R15: 0000000000000003
[  184.862714] FS:  0000000000000000(0000) GS:ffff8eb6f6c40000(0000) knlGS:0000000000000000
[  184.862723] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  184.862733] CR2: ffffffffffffffd6 CR3: 000000002f60a001 CR4: 00000000003706e0
[  184.862743] Call Trace:
[  184.862751]  <IRQ>
[  184.862759]  ath11k_dp_rx_h_ppdu+0x210/0x350 [ath11k]
[  184.862841]  ath11k_dp_rx_process_received_packets+0x1e6/0x6b0 [ath11k]
[  184.862891]  ath11k_dp_process_rx+0x32d/0x3e0 [ath11k]

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1

Fixes: b3febdcc ("ath11k: add LDPC FEC type in 802.11 radiotap header")
Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220126010144.2090-1-quic_bqiang@quicinc.com