atmel_lcdfb: disallow setting larger resolution than the framebuffer memory can handle

Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Krzysztof Helt <krzysztof.h1@wp.pl>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>