wifi: ath11k: fix temperature event locking

The ath11k active pdevs are protected by RCU but the temperature event
handling code calling ath11k_mac_get_ar_by_pdev_id() was not marked as a
read-side critical section as reported by RCU lockdep:

	=============================
	WARNING: suspicious RCU usage
	6.6.0-rc6 #7 Not tainted
	-----------------------------
	drivers/net/wireless/ath/ath11k/mac.c:638 suspicious rcu_dereference_check() usage!

	other info that might help us debug this:

	rcu_scheduler_active = 2, debug_locks = 1
	no locks held by swapper/0/0.
	...
	Call trace:
	...
	 lockdep_rcu_suspicious+0x16c/0x22c
	 ath11k_mac_get_ar_by_pdev_id+0x194/0x1b0 [ath11k]
	 ath11k_wmi_tlv_op_rx+0xa84/0x2c1c [ath11k]
	 ath11k_htc_rx_completion_handler+0x388/0x510 [ath11k]

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

Tested-on: WCN6855 hw2.1 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.23

Fixes: a41d1034 ("ath11k: add thermal sensor device support")
Cc: stable@vger.kernel.org      # 5.7
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/20231019153115.26401-2-johan+linaro@kernel.org

drivers/net/wireless/ath/ath11k/wmi.c

@@ -8382,15 +8382,19 @@ ath11k_wmi_pdev_temperature_event(struct ath11k_base *ab,
 	ath11k_dbg(ab, ATH11K_DBG_WMI, "event pdev temperature ev temp %d pdev_id %d\n",
 		   ev->temp, ev->pdev_id);
 
+	rcu_read_lock();
+
 	ar = ath11k_mac_get_ar_by_pdev_id(ab, ev->pdev_id);
 	if (!ar) {
 		ath11k_warn(ab, "invalid pdev id in pdev temperature ev %d", ev->pdev_id);
-		kfree(tb);
-		return;
+		goto exit;
 	}
 
 	ath11k_thermal_event_temperature(ar, ev->temp);
 
+exit:
+	rcu_read_unlock();
+
 	kfree(tb);
 }