mmc: sh_mobile_sdhi: Add r7s72100 support

Add support for r7s72100 SoC.

Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>