mmc: block: Disable Command Queue while RPMB is used

RPMB does not allow Command Queue commands. Disable and re-enable the
Command Queue when switching.

Note that the driver only switches partitions when the queue is empty.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>