wifi: ath12k: Pass ab pointer directly to ath12k_dp_tx_get_encap_type()

wifi: ath12k: Pass ab pointer directly to ath12k_dp_tx_get_encap_type()

In ath12k_dp_tx_get_encap_type(), the arvif parameter is only used to
retrieve the ab pointer. In vdev delete sequence the arvif->ar could
become NULL and that would trigger kernel panic.
Since the caller ath12k_dp_tx() already has a valid ab pointer, pass it
directly to avoid panic and unnecessary dereferencing.

PC points to "ath12k_dp_tx+0x228/0x988 [ath12k]"
LR points to "ath12k_dp_tx+0xc8/0x988 [ath12k]".
The Backtrace obtained is as follows:
ath12k_dp_tx+0x228/0x988 [ath12k]
ath12k_mac_tx_check_max_limit+0x608/0x920 [ath12k]
ieee80211_process_measurement_req+0x320/0x348 [mac80211]
ieee80211_tx_dequeue+0x9ac/0x1518 [mac80211]
ieee80211_tx_dequeue+0xb14/0x1518 [mac80211]
ieee80211_tx_prepare_skb+0x224/0x254 [mac80211]
ieee80211_xmit+0xec/0x100 [mac80211]
__ieee80211_subif_start_xmit+0xc50/0xf40 [mac80211]
ieee80211_subif_start_xmit+0x2e8/0x308 [mac80211]
netdev_start_xmit+0x150/0x18c
dev_hard_start_xmit+0x74/0xc0

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00173-QCAHKSWPL_SILICONZ-1

Fixes: e93bbd65547e ("wifi: ath12k: fix packets are sent in native wifi mode while we set raw mode")
Signed-off-by: Tamizh Chelvam Raja <tamizh.raja@oss.qualcomm.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20250606044936.3989400-1-tamizh.raja@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>