wifi: ath11k: thermal: don't try to register multiple times

Every time the firmware boots we call ath11k_core_qmi_firmware_ready() which
ends up calling ath11k_thermal_register(). So we try to register thermal
devices multiple times. And when we power off the firmware during
suspend/hibernation (implemented in the next patch) we get a warning in resume:

hwmon hwmon4: PM: parent phy0 should not be sleeping

Workaround this similarly like ath11k_mac_register() does by testing
ATH11K_FLAG_REGISTERED.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.30
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
Link: https://msgid.link/20240221024725.10057-6-quic_bqiang@quicinc.com

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

 // SPDX-License-Identifier: BSD-3-Clause-Clear
 /*
  * Copyright (c) 2020 The Linux Foundation. All rights reserved.
- * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) 2022-2024 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 
 #include <linux/device.h>
@@ -163,6 +163,9 @@ int ath11k_thermal_register(struct ath11k_base *ab)
 	struct ath11k_pdev *pdev;
 	int i, ret;
 
+	if (test_bit(ATH11K_FLAG_REGISTERED, &ab->dev_flags))
+		return 0;
+
 	for (i = 0; i < ab->num_radios; i++) {
 		pdev = &ab->pdevs[i];
 		ar = pdev->ar;