wifi: ath11k: fix gtk offload status event locking

The ath11k active pdevs are protected by RCU but the gtk offload status
event handling code calling ath11k_mac_get_arvif_by_vdev_id() was not
marked as a read-side critical section.

Mark the code in question as an RCU read-side critical section to avoid
any potential use-after-free issues.

Compile tested only.

Fixes: a16d9b50 ("ath11k: support GTK rekey offload")
Cc: stable@vger.kernel.org      # 5.18
Cc: Carl Huang <quic_cjhuang@quicinc.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20231019155342.31631-1-johan+linaro@kernel.org