drivers: video: fbdev: atmel_lcdfb.c: remove unnecessary header

Remove unnecessary mach/cpu.h header to be able to converge to a multiplatform
kernel.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>