Otherwise expr_evaluate_value() fails with invalid datatype:
# nft --debug=netlink add rule ip x y 'ct mark set ip dscp & 0x0f << 1'
BUG: invalid basetype invalid
nft: evaluate.c:440: expr_evaluate_value: Assertion `0' failed.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>