arm: rmobile: rcar: Add support ext2 and ext4 file system

Board with R-Car SoC has USB and MMC. They might use the EXT2 or EXT4 file system.
This adds support ext2 and ext4 file system

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