ath11k: Fix some resource leaks in error path in 'ath11k_thermal_register()'

If 'thermal_cooling_device_register()' fails, we must undo what has been
allocated so far. So we must go to 'err_thermal_destroy' instead of
returning directly

In case of error in 'ath11k_thermal_register()', the previous
'thermal_cooling_device_register()' call must also be undone. Move the
'ar->thermal.cdev = cdev' a few lines above in order for this to be done
in 'ath11k_thermal_unregister()' which is called in the error handling
path.

Fixes: 2a63bbca ("ath11k: add thermal cooling device support")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200513201454.258111-1-christophe.jaillet@wanadoo.fr