mwl8k: Recover from firmware crash

In case of firmware crash, reload the firmware and reconfigure it
by triggering ieee80211_hw_restart; mac80211 utility function.

V2 Addressed following comments from Lennert:
 - Stop the queues during reload
 - Removed atomic_t declaration for hw_restart
 - Extend the firmware reload support for sta firmware as well
 - Other misc changes

Signed-off-by: Nishant Sarmukadam <nishants@marvell.com>
Signed-off-by: Yogesh Ashok Powar <yogeshp@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>