drm/amd/display: Report non-DP display as disconnected without EDID

[Why]
Some boards seem to have a problem where HPD is high on HDMI even though
no display is connected. We don't want to report these as connected. DP
spec still requires us to report DP displays as connected when HPD is
high but we can't read the EDID in order to go to fail-safe mode.

[How]
If connector_signal is not DP abort detection if we can't retrieve the
EDID.

v2: Add Bugzilla and stable

Bugzilla: https://bugs.freedesktop.org/107390
Bugzilla: https://bugs.freedesktop.org/106846


Cc: stable@vger.kernel.org
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>