mmc: sh_sdhi: Add DM and DT probing support

mmc: sh_sdhi: Add DM and DT probing support

Add MMC DM and DT probing support into the SH SDHI driver.
This patch abstracts out the common bits of the send command
and set ios functions, so they can be used both by DM and non
DM setups and adds the DM probe support.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>