mt76: move mt76x02_init_device in mt76x02-lib module

Move mt76x02_init_device routine in mt76x02_util.c in order to be
reused by mt76x0 driver and remove duplicated code. Move interface
combo definition supported by the driver in mt76x02_init_device routine

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>