drm/amd/display: Handle get crtc position error

[Why]
dc_stream_get_crtc_position can return false.
This was unhandled in delay_cursor_until_vupdate

[How]
If dc_stream_get_crtc_position returns false, something
is weird.  Don't delay.
Signed-off-by: David Francis <David.Francis@amd.com>
Reviewed-by: Sun peng Li <Sunpeng.Li@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/core/dc_stream.c

@@ -211,7 +211,8 @@ static void delay_cursor_until_vupdate(struct pipe_ctx *pipe_ctx, struct dc *dc)
 			ASIC_REV_IS_RAVEN(stream->ctx->asic_id.hw_internal_rev)) {
 
 		vupdate_line = get_vupdate_offset_from_vsync(pipe_ctx);
-		dc_stream_get_crtc_position(dc, &stream, 1, &vpos, &nvpos);
+		if (!dc_stream_get_crtc_position(dc, &stream, 1, &vpos, &nvpos))
+			return;
 
 		if (vpos >= vupdate_line)
 			return;