drm/i915: Add aspect ratio property for HDMI

Create and attach the drm property to set aspect ratio. If there is no user
specified value, then PAR_NONE/Automatic option is set by default. User can
select aspect ratio 4:3 or 16:9. The aspect ratio selected by user would
come into effect with a mode set.

v2: Modified switch case to include aspect ratio enum changes

v3: Modified the patch according the change in the earlier patch to return
errno in case property creation fails. With this change, property will be
attached only if creation is successful

Signed-off-by: Vandana Kannan <vandana.kannan@intel.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>