ARM: exynos: Add fb_videomode structure to FIMD for snow,daisy and smdk

ARM: exynos: Add fb_videomode structure to FIMD for snow,daisy and smdk

Add extra mode of 1280x720 as a common mode between HDMI and
FIMD which will be used in clone mode scenario.

BUG=chrome-os-partner:10851
TEST=used xrandr tool to switch LCD display resolution
     between 1366x768 and 1280x720 on snow.

Change-Id: I82aa5e0e86c0471f13aeb15f834239f2759b6019
Signed-off-by: Shirish S <s.shirish@samsung.com>
Reviewed-on: https://gerrit.chromium.org/gerrit/26846
Reviewed-by: Mandeep Singh Baines <msb@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>