drm/edid: Add API to help find connection type

To fill the audio infoframe it is required to identify the
connection type as DP or HDMI. This patch adds an API which
parses ELD and returns the display type connected.

Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: dri-devel@lists.freedesktop.org
Cc: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>