drm/amd/display: Fix ASSR enablement on DP to EDP converter

drm/amd/display: Fix ASSR enablement on DP to EDP converter

ASSR mode is not enable when we connect eDP panel via DP to eDP converter.
connector_signal is coming as SIGNAL_TYPE_DISPLAY_PORT. Present code
ignoring panel_mode_edp for SIGNAL_TYPE_DISPLAY_PORT. Added checking
panel_mode_edp for all signals.

Signed-off-by: Ayyappa Chandolu <Ayyappa.Chandolu@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>