netfilter: nf_tables: improve UAPI kernel-doc comments

netfilter: nf_tables: improve UAPI kernel-doc comments

In include/uapi/linux/netfilter/nf_tables.h,
correct the kernel-doc comments for mistyped enum names and enum values to
avoid these kernel-doc warnings and improve the documentation:

nf_tables.h:896: warning: Enum value 'NFT_EXTHDR_OP_TCPOPT' not described
 in enum 'nft_exthdr_op'
nf_tables.h:896: warning: Excess enum value 'NFT_EXTHDR_OP_TCP' description
 in 'nft_exthdr_op'

nf_tables.h:1210: warning: expecting prototype for enum
 nft_flow_attributes. Prototype was for enum nft_offload_attributes instead

nf_tables.h:1428: warning: expecting prototype for enum nft_reject_code.
 Prototype was for enum nft_reject_inet_code instead

(add beginning '@' to each enum value description:)
nf_tables.h:1493: warning: Enum value 'NFTA_TPROXY_FAMILY' not described
 in enum 'nft_tproxy_attributes'
nf_tables.h:1493: warning: Enum value 'NFTA_TPROXY_REG_ADDR' not described
 in enum 'nft_tproxy_attributes'
nf_tables.h:1493: warning: Enum value 'NFTA_TPROXY_REG_PORT' not described
 in enum 'nft_tproxy_attributes'

nf_tables.h:1796: warning: expecting prototype for enum
 nft_device_attributes. Prototype was for enum
 nft_devices_attributes instead

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>