ARM: OMAP2+: Fix compile error when FB_OMAP2 is not set

Otherwise we will get:

arch/arm/plat-omap/fb.c:101: error: expected ‘)’ before ‘*’ token
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

arch/arm/plat-omap/fb.c

@@ -98,6 +98,8 @@ arch_initcall(omap_init_fb);
 
 #else
 
-void __init omapfb_set_lcd_config(omap_lcd_config *config) { }
+void __init omapfb_set_lcd_config(const struct omap_lcd_config *config)
+{
+}
 
 #endif