wifi: ath12k: Introduce check against zero for ahvif->key_cipher in ath12k_mac_op_tx()

wifi: ath12k: Introduce check against zero for ahvif->key_cipher in ath12k_mac_op_tx()

Currently, ahvif->key_cipher is compared with the enum value
(WMI_CIPHER_NONE) inside ath12k_mac_op_tx(). However, ahvif->key_cipher is
set using the macro value WLAN_CIPHER_SUITE_XXXX which seems inconsistent.

To improve code consistency and readability, introduce check against zero
for ahvif->key_cipher instead of comparing it with the enum
(WMI_CIPHER_NONE).

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00209-QCAHKSWPL_SILICONZ-1

Signed-off-by: Aaradhana Sahu <aaradhana.sahu@oss.qualcomm.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20250403082207.3323938-3-aaradhana.sahu@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>