wifi: ath12k: fix dfs-radar and temperature event locking

The ath12k active pdevs are protected by RCU but the DFS-radar and
temperature event handling code calling ath12k_mac_get_ar_by_pdev_id()
was not marked as a read-side critical section.

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

Note that the temperature event handler looks like a place holder
currently but would still trigger an RCU lockdep splat.

Compile tested only.

Fixes: d8899132 ("wifi: ath12k: driver for Qualcomm Wi-Fi 7 devices")
Cc: stable@vger.kernel.org	# v6.2
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/20231019113650.9060-2-johan+linaro@kernel.org