wifi: mt76: mt7925: refine the txpower initialization flow

Refactor the initialization and reset flow for tx power setting to
eliminate redundant configurations

Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Link: https://patch.msgid.link/20250908071245.1833006-1-mingyen.hsieh@mediatek.com


Signed-off-by: Felix Fietkau <nbd@nbd.name>