wifi: mac80211_hwsim: Rename pid to portid to avoid confusion

wifi: mac80211_hwsim: Rename pid to portid to avoid confusion

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 15e473046cb6 ("netlink: Rename pid to portid to avoid confusion")

Signed-off-by: Jaewan Kim <jaewan@google.com>
Link: https://lore.kernel.org/r/20230130022252.1514647-1-jaewan@google.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>