Implement remove_interface and stop functionality

Send DEL_STA_SELF on remove_interface and STOP when driver is stopped.

Signed-off-by: Eugene Krasnikov <k.eugene.e@gmail.com>
Declare WLAN_NV_FILE as MODULE_FIRMWARE

Make appear WLAN_NV_FILE in modinfo

Signed-off-by: Eugene Krasnikov <k.eugene.e@gmail.com>