The building of elements is really mess, and really the only
reason we're not doing it in SKBs in the first place is that
the scan code in ieee80211_build_preq_ies() doesn't.

Convert ieee80211_build_preq_ies() to use an SKB internally
so that we can gradually convert other things to ..._put_*()
style interfaces.

Link: https://msgid.link/20240129202041.c3a8e3c2cc99.I9d9920858c30ae5154719783933de0d7bc2a2cb9@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>