fbdev: sh_mobile_lcdc: Turn dot clock on before resuming from runtime PM

Resuming from runtime PM restores all LCDC registers. If the dot clock
is off at that time display panning information will be corrupted.

Turn the dot clock on before resuming from runtime PM. Similarly,
turn the clock off after suspending the LCDC.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>