drm/amd/display: Refine error message for vblank init failure

[Why]
The error message "failed to initialize sw for display support" is used
for both DRM device and vblank initialization failures, making it difficult
to identify the specific failure during troubleshooting.

[How]
Update the vblank initialization error message to
"failed to initialize vblank for display support"
to distinguish it from the DRM device init failure.

Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Roman Li

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

@@ -2186,7 +2186,7 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 
 	if (drm_vblank_init(adev_to_drm(adev), adev->dm.display_indexes_num)) {
 		drm_err(adev_to_drm(adev),
-		"failed to initialize sw for display support.\n");
+		"failed to initialize vblank for display support.\n");
 		goto error;
 	}