drm/amdgpu: explicitly set pg_flags for ST

No need to retain previous settings as this is the first time
we set pg_flags.  Probably a copy/paste typo from the CZ code.
Avoids confusion.

No change in behavior as adev is kzallocated.
Reviewed-by: NTom St Denis <tom.stdenis@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/vi.c

@@ -1651,7 +1651,7 @@ static int vi_common_early_init(void *handle)
 			AMD_CG_SUPPORT_SDMA_MGCG |
 			AMD_CG_SUPPORT_SDMA_LS |
 			AMD_CG_SUPPORT_VCE_MGCG;
-		adev->pg_flags |= AMD_PG_SUPPORT_GFX_PG |
+		adev->pg_flags = AMD_PG_SUPPORT_GFX_PG |
 			AMD_PG_SUPPORT_GFX_SMG |
 			AMD_PG_SUPPORT_GFX_PIPELINE |
 			AMD_PG_SUPPORT_UVD |