ath6kl: Fix disconnect event reporting

Driver does not report disconnect event properly when in connecting state,
this leads to issues failures in starting reconnection. Send a disconnect
command to target when a disconnect event is received with reason code
other than 3 (DISCONNECT_CMD - disconnect request from host) to make the
frimware stop trying to connect even after giving disconnect event. There
will be one more disconnect event for this disconnect command with reason
code DISCONNECT_CMD which will be notified to cfg80211.

Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>