mt76x0: init rx filter in mt76x0_init_hardware

Initialize rxfilter mask at bootstrap an not at mac start.
This is a preliminary patch to share mt76x2_mac_start routine
between mt76x2e and mt76x0e drivers

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