It is a frequent mistake to confuse the netlink port identifier with a
process identifier.  Try to reduce this confusion by renaming
that hold port identifiers portid instead of pid.

This change replicates following commit:
  commit 15e47304 ("netlink: Rename pid to portid to avoid confusion")
Signed-off-by: NJaewan Kim <jaewan@google.com>
Link: https://lore.kernel.org/r/20230130022252.1514647-1-jaewan@google.comSigned-off-by: NJohannes Berg <johannes.berg@intel.com>