Prefix UDP local function with a udp_ prefix to avoid confusion

[bz]

Summary

get_inpcbinfo() and get_pcblist() are UDP local functions and
do not do what one would expect by name. Prefix them with "udp_"
to at least obviously limit the scope.

Test Plan

builds.

[rwatson]

Although I have read through it and believe that the principle of this patch is a very good one, I have not, myself, tested it.

[gnn]

This is a purely textual change. Go for it.