Fixes problem where caller would think routine succeeded when it failed
leading to divide by zero panic.

(This also reverts an earlier attempt, commit 42bc0c97 "rtlwifi: Return
correct failure code on error". -- JWL)
Signed-off-by: Simon Graham <simon.graham@virtualcomputer.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>