ath10k: add wmi interface for pdev_get_temperature

Add WMI command support for reading temperature from the target and
corresponding WMI temperature event handler. The pdev_get_temperature
command is currently supported in 10.2 firmware alone.

Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>