drm: Add and handle new aspect ratios in DRM layer

HDMI 2.0/CEA-861-F introduces two new aspect ratios:
- 64:27
- 256:135

This patch:
-  Adds new DRM flags for to represent these new aspect ratios.
-  Adds new cases to handle these aspect ratios while converting
from user->kernel mode or vise versa.

V2: Rebase
V3: Align macro for DRM_MODE_PICTURE_ASPECT_256_135 (Jim Bride)
V4: Added r-b from Jose.

Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Jose Abreu <Jose.Abreu@synopsys.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1476705880-15600-5-git-send-email-shashank.sharma@intel.com