fbdev: remove dependency of FB_SH_MOBILE_MERAM from FB_SH_MOBILE_LCDC

MERAM can be used for other IP blocks as well in the future.
It doesn't necessarily mean that the MERAM driver depends on the LCDC.
This patch corrects dependency.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>