drm/amd/display: Add a function for checking tmds mode

[Why]
DVI is TMDS signal like HDMI but without audio.  Current signal check
does not correctly reflect DVI clock programming.

[How]
Define a new signal check for TMDS that includes DVI to HDMI TMDS
programming.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Chris Park <chris.park@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/include/signal_types.h

@@ -118,6 +118,19 @@ static inline bool dc_is_dvi_signal(enum signal_type signal)
 	}
 }
 
+static inline bool dc_is_tmds_signal(enum signal_type signal)
+{
+	switch (signal) {
+	case SIGNAL_TYPE_DVI_SINGLE_LINK:
+	case SIGNAL_TYPE_DVI_DUAL_LINK:
+	case SIGNAL_TYPE_HDMI_TYPE_A:
+		return true;
+	break;
+	default:
+		return false;
+	}
+}
+
 static inline bool dc_is_dvi_single_link_signal(enum signal_type signal)
 {
 	return (signal == SIGNAL_TYPE_DVI_SINGLE_LINK);