drm/amd/display: Use is_dig_enable function instead of dcn10 hardcode

[Why]
This can differ depending on ASIC and we can end up skipping all
transmitter control if we're relying on the wrong bit as a shortcut
for whether link is on/off.

[How]
The ASIC table itself provides the correct DIG check, use that instead
of the dcn10 hardcode.

Reviewed-by: Syed Hassan <syed.hassan@amd.com>
Acked-by: Alan Liu <haoping.liu@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_link_encoder.c

@@ -1056,7 +1056,7 @@ void dcn10_link_encoder_disable_output(
 	struct bp_transmitter_control cntl = { 0 };
 	enum bp_result result;
 
-	if (!dcn10_is_dig_enabled(enc)) {
+	if (enc->funcs->is_dig_enabled && !enc->funcs->is_dig_enabled(enc)) {
 		/* OF_SKIP_POWER_DOWN_INACTIVE_ENCODER */
 	/*in DP_Alt_No_Connect case, we turn off the dig already,
 	after excuation the PHY w/a sequence, not allow touch PHY any more*/

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_dio_link_encoder.c

@@ -558,7 +558,7 @@ void dcn31_link_encoder_disable_output(
 		struct dmub_cmd_dig_dpia_control_data dpia_control = { 0 };
 		struct dc_link *link;
 
-		if (!dcn10_is_dig_enabled(enc))
+		if (enc->funcs->is_dig_enabled && !enc->funcs->is_dig_enabled(enc))
 			return;
 
 		link = link_enc_cfg_get_link_using_link_enc(enc->ctx->dc, enc->preferred_engine);