netfilter: nf_tables: extended netlink error reporting for chain type

netfilter: nf_tables: extended netlink error reporting for chain type

Users that forget to select the NAT chain type in netfilter's Kconfig
hit ENOENT when adding the basechain.

This report is however sparse since it might be the table, the chain
or the kernel module that is missing/does not exist.

This patch provides extended netlink error reporting for the
NFTA_CHAIN_TYPE netlink attribute, which conveys the basechain type.
If the user selects a basechain that his custom kernel does not support,
the netlink extended error provides a more accurate hint on the
described issue.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>