icnss: reject idle restart if wlan driver unregistered

This change is to reject idle restart if wlan driver
unregistered or unregistration is in progress. Kernel
holds rtnl lock before calling interface up and wlan driver
needs same rtnl lock to complete driver unregister. In
scenerio's where idle rstart and wlan driver remove gets
called back to back, there is a possibility of deadlock.
So, with this change reject idle restart if wlan driver
is getting unregistered.

Change-Id: If6733a039d896cbd682af6ebbdccacc11107c03d
Signed-off-by: Sandeep Singh <sandsing@codeaurora.org>