video: ARM CLCD: Remove duplicated include in amba-clcd.c

This patch fixes duplicated include dma-mapping.h in
drivers/video/fbdev/amba-clcd.c

Signed-off-by: Qiang Chen <qiang2.chen@sonymobile.com>
Acked-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>