net: sntp: support building without NET_SOCKETS_POSIX_NAMES

Fixes the compiler error that occurs when attempting to build
the SNTP library with CONFIG_NET_SOCKETS_POSIX_NAMES=n, while
using native_posix.

Closes #57133

Co-authored-by: Chris Friedt <cfriedt@meta.com>
Signed-off-by: Hein Wessels <heinwessels93@gmail.com>