drm/radeon/si: add some missing regs to the VM reg checker

This register is needed for streamout to work properly.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
diff --git a/drivers/gpu/drm/radeon/si.c b/drivers/gpu/drm/radeon/si.c
index b0db712..4422d63 100644
--- a/drivers/gpu/drm/radeon/si.c
+++ b/drivers/gpu/drm/radeon/si.c
@@ -2474,6 +2474,7 @@
 	/* check config regs */
 	switch (reg) {
 	case GRBM_GFX_INDEX:
+	case CP_STRMOUT_CNTL:
 	case VGT_VTX_VECT_EJECT_REG:
 	case VGT_CACHE_INVALIDATION:
 	case VGT_ESGS_RING_SIZE: