ath10k: add hw connection monitor support

Some firmware revisions (e.g. qca6174 with fw73)
don't deliver beacons to host reliably. This
causes random disconnects even in perfect
conditions. This is most visible with
multi-channel operation.

All available firmware revisions seem to support
beacon miss offloading so there shouldn't be any
problems.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>