ARM: EXYNOS: Correct framebuffer window size on Nuri board

The real LCD resolution on Nuri is 1024x600, not 1280x800. This change
fixes the color distortion (green shadows) on half of the screen.
Also increase framebuffer virtual size for display panning support.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>