mwifiex: do not release lock during list_for_each_entry_safe()

As we are releasing the lock, during next iteration we may end
up getting page fault if other thread has already deleted that
node.

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