staging: wilc1000: adds a cfg80211_disconnected() function

This patch is adds a cfg80211_disconnected() when connection is lost already.
We was find this situation while test the 'rmmod sdio'.
SDIO remove function are include both remove mac_close and unregister net_device.
That is received one more a disconnect cmd from cfg80211.
Driver was already performed disconnect.
If wilc->close value was set to true, adds a call to cfg80211_disconnected().

Signed-off-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>