video: fbdev: sh_mobile_lcdcfb: Remove sh_mobile_lcdc_check_var() declaration

As of commit 0fe66f32 ("fbdev/sh_mobile: remove
sh_mobile_lcdc_display_notify"), there is no longer a need for a foward
declaration of sh_mobile_lcdc_check_var().

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Helge Deller <deller@gmx.de>