mt76: mt7615: apply cached RF data for DBDC

Band0 and band1 share the same hardware, so band0 will stop Tx/Rx when
band1 performs Rx calibration. cal_cache is introduced to solve such
corner cases by moving necessary datas from channel_switch to bootup.

Co-developed-by: Peter Chiu <chui-hao.chiu@mediatek.com>
Signed-off-by: Peter Chiu <chui-hao.chiu@mediatek.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>