Currently, command path waits till all the tx host queues
are empty. Whenever watchdog event is raised, firmware
expects driver to destroy ampdu queues immediately.

This requires corresponding commands i.e.
mwl8k_cmd_get_watchdog_bitmap and mwl8k_destroy_ba to be
sent without waiting for the tx queues to be completely
empty.

Use "watchdog_event_pending" to ensure the above mentioned
two commands are sent down immediately.
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>