mt76: mt7921: enable HW beacon filter not depending on PM flag

The hardware beacon filter works whether or not the PM flag is set, so we
drop redundant dependency checks on PM flags.

Additionally, the patch implicitly allow the MT7921[E, S, U] to have a
consistent configuration of the hardware beacon filter.

Tested-by: Deren Wu <deren.wu@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>