arm: rmobile: lager: Add support MMC and MMC command

Lager board has been connected to eMMC of 8GB to MMC1 port.
This enables MMC1 port and MMC command.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>