drm/amd/display: prevent S4 test from failing

[why]
limit the vm prefetch check for now, until the feature is fully
verified.
Reviewed-by: Hansen Dsouza <Hansen.Dsouza@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn21/dcn21_hubbub.c

@@ -67,15 +67,9 @@ static uint32_t convert_and_clamp(
 void dcn21_dchvm_init(struct hubbub *hubbub)
 {
 	struct dcn20_hubbub *hubbub1 = TO_DCN20_HUBBUB(hubbub);
-	uint32_t riommu_active, prefetch_done;
+	uint32_t riommu_active;
 	int i;
 
-	REG_GET(DCHVM_RIOMMU_STAT0, HOSTVM_PREFETCH_DONE, &prefetch_done);
-
-	if (prefetch_done) {
-		hubbub->riommu_active = true;
-		return;
-	}
 	//Init DCHVM block
 	REG_UPDATE(DCHVM_CTRL0, HOSTVM_INIT_REQ, 1);