mt76x0: move mt76x0_init_hardware in mt76x0_register_device

Move mt76x0_init_hardware routine in mt76x0_register_device
during hw probe. This is a preliminary patch to avoid {tx/rx}
buffer allocation during resume/suspend

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