mt76: unify ampdu_action

Use mt76x2_ampdu_action as common function, mt76x0 ampdu_action was
diffrent, but mt76x2 version should work for this driver as well.

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