Move mt76x2_wait_for_bbp utility routine in mt76x02_util.h
in order to be resued by mt76x0 driver. Morover rename it in
mt76x02_wait_for_txrx_idle
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>