UPSTREAM: drm/edid: Reduce the number of times we parse the CEA extension block

UPSTREAM: drm/edid: Reduce the number of times we parse the CEA extension block

Instead of parsing parts of the CEA extension block in two places
to determine supported color formats and whatnot, let's just
consolidate it to one function. This also makes it possible to neatly
flatten drm_assign_hdmi_deep_color_info().

Change-Id: I68bd125757e6e5c8f13db62e52c4da827c040809
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1475070703-6435-7-git-send-email-ville.syrjala@linux.intel.com
Signed-off-by: Zheng Yang <zhengyang@rock-chips.com>
(cherry picked from commit 1cea146a806ae1f34cb1b5e3206ff63a2bb90782)