wifi: mt76: mt7921: move shared runtime-pm code on mt792x-lib

Moving hif_ops marcos in mt792x.h, we can move shared runtime-pm code
between mt7925 and mt7921 in mt792x-lib module.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>