[DECNET]: dn_nl_deladdr() almost always returns no error

As far as I see from the err variable initialization
the dn_nl_deladdr() routine was designed to report errors
like "EADDRNOTAVAIL" and probaby "ENODEV".

But the code sets this err to 0 after the first nlmsg_parse
and goes on, returning this 0 in any case.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>