mt76: mt7921: use physical addr to unify register access

Use physical address to unify the register access and reorder the
entries in fixed_map table to accelerate the address lookup for
MT7921e. Cosmetics the patch with adding an extra space to make all
entries in the array style consistent.

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