radeonsi: don't use PFP_SYNC_ME with compute-only contexts

Compute rings don't have PFP.

Fixes: a1378639ab "radeonsi: always use compute rings for clover on CI and newer (v2)"

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Tested-by: Jan Vesely <jan.vesely@rutgers.edu>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>

src/gallium/drivers/radeonsi/si_cp_dma.c

 	 * indices. If we wanted to execute CP DMA in PFP, this packet
 	 * should precede it.
 	 */
-	if (flags & CP_DMA_PFP_SYNC_ME) {
+	if (sctx->has_graphics && flags & CP_DMA_PFP_SYNC_ME) {
 		radeon_emit(cs, PKT3(PKT3_PFP_SYNC_ME, 0, 0));
 		radeon_emit(cs, 0);
 	}