rtl8187: Fix error returns

There are two places in the rtl8187 code where a routine was returning zero
(OK) when it should have been returning an error.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>