fbdev: sh_mobile_hdmi: Don't access LCDC fb_info

The LCDC fb_info structure is only used to retrieve the default video
mode in case none of the modes advertised by EDID information is
acceptable. Pass a pointer to the default mode through the
sh_mobile_lcdc_entity structure instead.

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