datatype: Display pre-defined inet_service values in host byte order

datatype: Display pre-defined inet_service values in host byte order

nft describe displays, to the user, which values are available for a selector,
then the values should be in host byte order.

Variable size was replaced by len to better match the common pattern.

Reported-by: Pablo Neira Ayuso <pablo@netfilter.org>
Fixes: ccc5da470e76 ("datatype: Replace getnameinfo() by internal lookup table")
Signed-off-by: Elise Lennion <elise.lennion@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>