mmc: sdhci: Ensure all requests get errored out

In order to support commands during data transfer, there will have to be up
to two active requests (mrqs) at a time, instead of just one. That means
ensuring that all requests get errored out in the cases of card or driver
removal.

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