mmc: sdhci: Track whether a reset is pending

SDHCI recovers from errors by resetting the cmd and data circuits. Until
that is done, there very well might be more interrupts, so ignore them in
that case.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>