rtnetlink: Use nlmsg type RTM_NEWNEIGH from dflt fdb dump

rtnetlink: Use nlmsg type RTM_NEWNEIGH from dflt fdb dump

Change the dflt fdb dump handler to use RTM_NEWNEIGH to
be compatible with bridge dump routines.

The dump reply from the network driver handlers should
match the reply from bridge handler. The fact they were
not in the ixgbe case was effectively a bug. This patch
resolves it.

Applications that were not checking the nlmsg type will
continue to work. And now applications that do check
the type will work as expected.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>