The avl_update_* functions are never used by ZFS and are therefore
being removed. They're barely even used in Illumos. Additionally,
simplify avl_add() by using a VERIFY which produces exactly the same
behavior under Linux.
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#6716