netfilter: nf_tables: nft_parse_register can return a negative value

netfilter: nf_tables: nft_parse_register can return a negative value

BugLink: https://bugs.launchpad.net/bugs/1969857
[ Upstream commit 6c6f9f31ecd47dce1d0dafca4bec8805f9bc97cd ]

Since commit 6e1acfa387b9 ("netfilter: nf_tables: validate registers
coming from userspace.") nft_parse_register can return a negative value,
but the function prototype is still returning an unsigned int.

Fixes: 6e1acfa387b9 ("netfilter: nf_tables: validate registers coming from userspace.")
Signed-off-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>