The err condition in post_req() is set to undo a call made to pre_req()
that hasn't been started yet.  The err condition is not set if an MMC
request returns an error.
Signed-off-by: NPer Forlin <per.forlin@linaro.org>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NChris Ball <cjb@laptop.org>