vxlan: fix check for migration of static entry

The check introduced by:
	commit 26a41ae6
	Author: stephen hemminger <stephen@networkplumber.org>
	Date:   Mon Jun 17 12:09:58 2013 -0700

	    vxlan: only migrate dynamic FDB entries

was not correct because it is checking flag about type of FDB
entry, rather than the state (dynamic versus static). The confusion
arises because vxlan is reusing values from bridge, and bridge is
reusing values from neighbour table, and easy to get lost in translation.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>