mmc: sdhci: Support cap_cmd_during_tfr requests

Now SDHCI supports commands during transfer, enable support for the core
API.

There are 3 small changes needed:

First, auto-CMD12 cannot be used with a cap_cmd_during_tfr request because
the host controller cannot expect the command line to be available.

Secondly, a cap_cmd_during_tfr request must not send a stop command, again
because the host controller cannot expect the command line to be available.

Thirdly, when a cap_cmd_during_tfr command completes, use
mmc_command_complete() to notify the upper layers that the command line is
now available for further commands.

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