fbdev: sh_mobile_lcdc: reconfigure the framebuffer, when free

Currently the sh_mobile_lcdc driver only reconfigures the hardware interface,
when a new monitor is plugged in. This patch adds support for dynamic
framebuffer reconfiguration, when no user is holding the framebuffer device
node open.

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