bonding: do failover when high prio link up

Currently, when a high prio link enslaved, or when current link down,
the high prio port could be selected. But when high prio link up, the
new active slave reselection is not triggered. Fix it by checking link's
prio when getting up. Making the do_failover after looping all slaves as
there may be multi high prio slaves up.

Reported-by: Liang Li <liali@redhat.com>
Fixes: 0a2ff7cc ("Bonding: add per-port priority for failover re-selection")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>