mt76: mt7921: enable HW beacon filter in the initialization stage

The current driver has worked with HW beacon filter and connection
monitor all the way, here we move the enablement into the initialization
stage like other HW features being done to get rid of others are
confused why these configurations would be changed at runtime.

We still leave a way to turn off these offload features in debugfs knobs
but that is just for debugging purposes.

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>