This enables the baseband watchdog events for the AR9003
family on ath9k. Upon an a baseband watchdog interrupt we reset
the hardware, this should address corner case conditions where
normal operation can stall. Enable ATH_DBG_RESET to be able
to review details of the bb watchdog interrupt once it happens.
If you're curious how often this happens just grep the debugfs
interrupt file.

Cc: Sam Ng <sam.ng@atheros.com>
Cc: Paul Shaw <paul.shaw@atheros.com>
Cc: Don Breslin <don.breslin@atheros.com>
Cc: Cliff Holden <cliff.holden@atheros.com
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com
Signed-off-by: John W. Linville <linville@tuxdriver.com>