Otherwise the field ends up being used uninitialized when
enabling modifiers, failing validation with high likelyhood.

v4: Use memset
Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
(for v1)
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>