[DECNET]: Fix level1 router hello

This patch fixes hello messages sent when a node is a level 1
router. Slightly contrary to the spec (maybe) VMS ignores hello
messages that do not name level2 routers that it also knows about.

So, here we simply name all the routers that the node knows about
rather just other level1 routers.  (I hope the patch is clearer than
the description. sorry).

Signed-off-by: Patrick Caulfield <patrick@tykepenguin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>