mwl8k: bump firmware API to 3

New firmware is required to support
a) Add support for additional ampdu streams
b) Handle corresponding watchdog events to destroy ampdu streams

Bumping firmware API version by one.

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>