fbdev: sh_mobile_lcdc: reduce scope of a variable

The "ret" variable in sh_mobile_lcdc_start() is only used at one
location, move its definition to the inner-most scope.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>