fbdev: sh_mobile_lcdc: use display information in info for panning

We must not use any information in the passed var besides xoffset,
yoffset and vmode as otherwise applications might abuse it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>