mmc: block: add checking of r/w command response

Check the status bits in the r/w command response for any errors.
If error bits are set, then we won't have seen any data transferred,
so it's pointless doing any further checking.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Chris Ball <cjb@laptop.org>