mfd/mmc: SDHI Kconfig update

Enable the sh_mobile_sdhi mfd driver on SH-Mobile ARM
processors. While at it, make CONFIG_TMIO_MMC depend on
CONFIG_MFD_SH_MOBILE_SDHI.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>