bridge: Add fdb dst check during fdb update

Current bridge fdb update code does not seem to update the port
during fdb update. This patch adds a check for fdb dst (port)
change during fdb update. Also rearranges the call to
fdb_notify to send only one notification for create and update.

Changelog:
v2 - Change notify flag to bool

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