mmc: sdhci: Do not reset cmd or data circuits that are in use

In order to support commands during data transfer, it will be possible to
need to reset the command circuit while the data circuit is in use, and
vice versa. It is now easy to determine whether the command or data circuit
is in use, and so just skip the corresponding reset if it is.

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