drm/amd/display: Fix compile error on older GCC versions

GCC 4.9 reports a 'missing braces around initializer' error. This is a
bug, documented here:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119

Fix it by adding another brace.
Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Reviewed-by: Mikita Lipski <Mikita.Lipski@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c

@@ -514,8 +514,8 @@ enum dc_edid_status dm_helpers_read_local_edid(
 				edid_status,
 				aconnector->base.name);
 	if (link->aux_mode) {
-		union test_request test_request = {0};
-		union test_response test_response = {0};
+		union test_request test_request = { {0} };
+		union test_response test_response = { {0} };
 
 		dm_helpers_dp_read_dpcd(ctx,
 					link,