mwifiex: reduce spinlock usage in main process

We will reset more_task_flag at the end of main process
routine. This optimization will help to remove spinlock
operations at couple of places in the code.

Signed-off-by: Cathy Luo <cluo@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>