mwl8k: Handle Watchdog events for the new ampdu streams

With more ampdu streams, we need to handle watchdog
events for the new ampdu streams. Handle these
events appropriately.

Earlier mwl8k_cmd_get_watchdog_bitmap used to return
only one stream index and hence bitwise operations
on the return value were not required. Now the function
returns a bitmap with different bits are mapped with
different stream indices.

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>