wil6210: report association ID (AID) per station in debugfs

Add reporting of the association ID (AID) for each station
as part of the stations file in the debugfs.
Valid AID values are 1-254. 0 is reported if the AID
is unknown or not reported by firmware.

Signed-off-by: Lior David <qca_liord@qca.qualcomm.com>
Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>