rtl8187: Add AD-HOC support

Add AD-HOC support to the rtl8187 based on the rtl8180 source

Signed-off-by: Attila Fazekas <turul64@gmail.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>