drm/amd/display: Fetch the EDID from _DDC if available for eDP

Some manufacturers have intentionally put an EDID that differs from
the EDID on the internal panel on laptops.

Attempt to fetch this EDID if it exists and prefer it over the EDID
that is provided by the panel. If a user prefers to use the EDID from
the panel, offer a DC debugging parameter that would disable this.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>