drm/amd/display: Disable DSC power gating in Diags

[why]
With DSC power gating enabled, one of the register reads times out occasionally,
causing a DSC test to fail.

[how]
Disable DSC power gating in Diags.
NOTE: This has to be reverted once the problems with DSC power gating are
resolved.
Signed-off-by: Nikola Cornij <nikola.cornij@amd.com>
Reviewed-by: Nevenko Stupar <Nevenko.Stupar@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

@@ -723,6 +723,9 @@ static const struct dc_debug_options debug_defaults_diags = {
 		.disable_pplib_wm_range = true,
 		.disable_stutter = true,
 		.scl_reset_length10 = true,
+#ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
+		.disable_dsc_power_gate = true,
+#endif
 };
 
 void dcn20_dpp_destroy(struct dpp **dpp)