ath6kl: Recover from fw crash

Re-initialize the target when fw crash is reported.
This would make the device functional again after
target crash. During the target re-initialization
it is made sure that target is not bugged with data/cmd
request, ar->state ATH6KL_STATE_RECOVERY is used
for this purpose.

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