rtl8187: fix typo in ifdef comment

Cc: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>