staging: rtl8723au: Introduce rtw_select_candidate_from_queue()

This splits a portion of rtw_select_and_join_from_scanned_queue23a()
into rtw_select_candidate_from_queue()

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>