sh: ms7724se: add 1280x720 lcdc output support

There was no big meaning in the support of SVGA,
but 720p support is necessary for ms7724se board.
So, this patch support 720p instead of SVGA.

Signed-off-by: Kuninori Morimoto <morimoto.kuninori@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>