wifi: ath12k: Remove ath12k_get_num_hw() helper function

wifi: ath12k: Remove ath12k_get_num_hw() helper function

Currently, the ath12k_get_num_hw() helper function takes the device handle
as an argument. Here, the number of hardware is retrieved from the group
handle. Demanding the device handle from the caller is unnecessary since
in some cases the group handle is already available. Additionally, there
is no longer a need for multiple indirections to get the number of
hardware. Therefore, remove this helper function and directly use
ag->num_hw. This change also fixes the below Smatch static checker
warning.

Smatch warning:
ath12k_mac_destroy() error: we previously assumed 'ab' could be null

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

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/ath12k/3e705de0-67d1-4437-97ff-4828d83ae2af@stanley.mountain/
Closes: https://scan7.scan.coverity.com/#/project-view/52682/11354?selectedIssue=1602340
Fixes: a343d97f27f5 ("wifi: ath12k: move struct ath12k_hw from per device to group")
Signed-off-by: Karthikeyan Periyasamy <quic_periyasa@quicinc.com>
Acked-by: Kalle Valo <kvalo@kernel.org>
Acked-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>
Link: https://patch.msgid.link/20250112071630.4059410-4-quic_periyasa@quicinc.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>