drm/amd/display: Remove a false-positive error message

To avoid confusion, need to suppress the error message when get
-ERESTARTSYS error code. It is normal when getting interrupted
by signals in the process of a wait for the buffer to become
unreserved. Only propagate to user-mode for further action,
no need to pop up error message.
Signed-off-by: Jerry Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Sun peng Li <Sunpeng.Li@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.c

@@ -1790,7 +1790,9 @@ static int get_fb_info(const struct amdgpu_framebuffer *amdgpu_fb,
 	int r = amdgpu_bo_reserve(rbo, false);
 
 	if (unlikely(r)) {
-		DRM_ERROR("Unable to reserve buffer\n");
+		// Don't show error msg. when return -ERESTARTSYS
+		if (r != -ERESTARTSYS)
+			DRM_ERROR("Unable to reserve buffer: %d\n", r);
 		return r;
 	}