drm/amd/display: add hdmi disable debug check

[Why]
Using the hdmi_disable option doesnt disable 6GB bandwidth

[How]
Add debug.hdmi20_disable flage when checking 6GB enable or not.
Reviewed-by: Chris Park <Chris.Park@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Dale Zhao <dale.zhao@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/dce/dce_link_encoder.c

@@ -788,7 +788,8 @@ static bool dce110_link_encoder_validate_hdmi_output(
 			crtc_timing->pixel_encoding == PIXEL_ENCODING_YCBCR420)
 		return false;
 
-	if (!enc110->base.features.flags.bits.HDMI_6GB_EN &&
+	if ((!enc110->base.features.flags.bits.HDMI_6GB_EN ||
+			enc110->base.ctx->dc->debug.hdmi20_disable) &&
 			adjusted_pix_clk_khz >= 300000)
 		return false;
 	if (enc110->base.ctx->dc->debug.hdmi20_disable &&

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

@@ -646,7 +646,8 @@ static bool dcn10_link_encoder_validate_hdmi_output(
 			crtc_timing->pixel_encoding == PIXEL_ENCODING_YCBCR420)
 		return false;
 
-	if (!enc10->base.features.flags.bits.HDMI_6GB_EN &&
+	if ((!enc10->base.features.flags.bits.HDMI_6GB_EN ||
+			enc10->base.ctx->dc->debug.hdmi20_disable) &&
 			adjusted_pix_clk_100hz >= 3000000)
 		return false;
 	if (enc10->base.ctx->dc->debug.hdmi20_disable &&