Move mt76x02_phy_set_bw routine in mt76x02_phy.c since
it is shared between mt76x0 and mt76x2 drivers and remove
duplicated code
Signed-off-by: NLorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: NFelix Fietkau <nbd@nbd.name>