fbdev: sh-mobile-lcdc: fix potential Oops in SH-Mobile LCDC framebuffer driver

sh_mobile_lcdc_setup_clocks() can perform IO, therefore it has to be called
after ioremap(). Also check return code of ioremap() and use resource_size()
instead of open-coding it.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>