fbdev: sh_mobile_meram: Add _cfg suffix to struct sh_mobile_meram_icb

The structure describe ICB configuration, no ICB objects themselves.
Rename it to sh_mobile_meram_icb_cfg in preparation for the addition of
an ICB structure.

All the structure fields are unsigned integers, make them so.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>