wifi: mt76: mt7915: rework init flow in mt7915_thermal_init()

If kernel do not enable CONFIG_HWMON, it may cause thermal
initialization to be done with temperature value 0 and then can not
transmit. This commit fixes it by setting trigger/restore temperature
before checking CONFIG_HWMON.

Fixes: 7d12b38a ("wifi: mt76: mt7915: call mt7915_mcu_set_thermal_throttling() only after init_work")
Signed-off-by: Howard Hsu <howard-yh.hsu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>