Introduce mt76_skb_adjust_pad to reuse the code adding sdio support to
mt7615 driver and remove code duplication. Move 4B header configuration
for usb devices out of mt76_skb_adjust_pad
Signed-off-by: NLorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: NFelix Fietkau <nbd@nbd.name>