mt76: mt7615: use full on-chip memory address for WF_PHY registers

mt76: mt7615: use full on-chip memory address for WF_PHY registers

Now that the bus access functions can use mapping for accessing full
register addresses, use it for WF_PHY registers to keep them constant.
Needed for follow-up work on testmode support

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