vxlan: dont migrate permanent fdb entries during learn

[ Upstream commit e0090a9e979de5202c7d16c635dea2f005221073 ]

This patch fixes vxlan_snoop to not move permanent fdb entries
on learn events. This is consistent with the bridge fdb
handling of permanent entries.

Fixes: 26a41ae6 ("vxlan: only migrate dynamic FDB entries")
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>