mt76: fix return value of mt76x02_wait_for_mac

We need to return bool value in mt76x02_wait_for_mac.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 2735a6dd

 ("mt76: unify wait_for_mac")
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>