ath11k: Fix crash caused by uninitialized TX ring

Commit 3158237 ("ath11k: Change number of TCL rings to one for
QCA6390") avoids initializing the other entries of dp->tx_ring cause
the corresponding TX rings on QCA6390/WCN6855 are not used, but leaves
those ring masks in ath11k_hw_ring_mask_qca6390.tx unchanged. Normally
this is OK because we will only get interrupts from the first TX ring
on these chips and thus only the first entry of dp->tx_ring is involved.

In case of one MSI vector, all DP rings share the same IRQ. For each
interrupt, all rings have to be checked, which means the other entries
of dp->tx_ring are involved. However since they are not initialized,
system crashes.

Fix this issue by simply removing those ring masks.

crash stack:
[  102.907438] BUG: kernel NULL pointer dereference, address: 0000000000000028
[  102.907447] #PF: supervisor read access in kernel mode
[  102.907451] #PF: error_code(0x0000) - not-present page
[  102.907453] PGD 1081f0067 P4D 1081f0067 PUD 1081f1067 PMD 0
[  102.907460] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI
[  102.907465] CPU: 0 PID: 3511 Comm: apt-check Kdump: loaded Tainted: G            E     5.15.0-rc4-wt-ath+ #20
[  102.907470] Hardware name: AMD Celadon-RN/Celadon-RN, BIOS RCD1005E 10/08/2020
[  102.907472] RIP: 0010:ath11k_dp_tx_completion_handler+0x201/0x830 [ath11k]
[  102.907497] Code: 3c 24 4e 8d ac 37 10 04 00 00 4a 8d bc 37 68 04 00 00 48 89 3c 24 48 63 c8 89 83 84 18 00 00 48 c1 e1 05 48 03 8b 78 18 00 00 <8b> 51 08 89 d6 83 e6 07 89 74 24 24 83 fe 03 74 04 85 f6 75 63 41
[  102.907501] RSP: 0000:ffff9b7340003e08 EFLAGS: 00010202
[  102.907505] RAX: 0000000000000001 RBX: ffff8e21530c0100 RCX: 0000000000000020
[  102.907508] RDX: 0000000000000000 RSI: 00000000fffffe00 RDI: ffff8e21530c1938
[  102.907511] RBP: ffff8e21530c0000 R08: 0000000000000001 R09: 0000000000000000
[  102.907513] R10: ffff8e2145534c10 R11: 0000000000000001 R12: ffff8e21530c2938
[  102.907515] R13: ffff8e21530c18e0 R14: 0000000000000100 R15: ffff8e21530c2978
[  102.907518] FS:  00007f5d4297e740(0000) GS:ffff8e243d600000(0000) knlGS:0000000000000000
[  102.907521] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  102.907524] CR2: 0000000000000028 CR3: 00000001034ea000 CR4: 0000000000350ef0
[  102.907527] Call Trace:
[  102.907531]  <IRQ>
[  102.907537]  ath11k_dp_service_srng+0x5c/0x2f0 [ath11k]
[  102.907556]  ath11k_pci_ext_grp_napi_poll+0x21/0x70 [ath11k_pci]
[  102.907562]  __napi_poll+0x2c/0x160
[  102.907570]  net_rx_action+0x251/0x310
[  102.907576]  __do_softirq+0x107/0x2fc
[  102.907585]  irq_exit_rcu+0x74/0x90
[  102.907593]  common_interrupt+0x83/0xa0
[  102.907600]  </IRQ>
[  102.907601]  asm_common_interrupt+0x1e/0x40

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

Signed-off-by: Baochen Qiang <bqiang@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211026011605.58615-1-quic_bqiang@quicinc.com

drivers/net/wireless/ath/ath11k/hw.c

@@ -1061,8 +1061,6 @@ const struct ath11k_hw_ring_mask ath11k_hw_ring_mask_ipq8074 = {
 const struct ath11k_hw_ring_mask ath11k_hw_ring_mask_qca6390 = {
 	.tx  = {
 		ATH11K_TX_RING_MASK_0,
-		ATH11K_TX_RING_MASK_1,
-		ATH11K_TX_RING_MASK_2,
 	},
 	.rx_mon_status = {
 		0, 0, 0, 0,