icnss: Clear driver ops during driver unload

As part of wlan driver unload wlan driver is freeing driver
ops memory on its side. ICNSS driver doesn't call wlan driver
remove if it is not probed. So, In some cases when wlan driver
has not been probed and driver unload comes,icnss driver doesn't
clears driver ops on its side which leads of freed memory
access on its side. This change clears wlan driver ops during
driver unload if wlan driver is not probed.

Change-Id: Idb03725b2c0b1bf68337badc82e40b1633bfcaa5
Signed-off-by: Sandeep Singh <sandsing@codeaurora.org>