sh: fix a number of Oopses and leaks in SH framebuffer driver

Fix a number of Oopses, memory leaks and unbalanced calls on error paths in
sh_mobile_lcdcfb.c.

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