net: Fix definition of netif_vdbg() when VERBOSE_DEBUG is defined

netif_vdbg() was originally defined as entirely equivalent to
netdev_vdbg(), but I assume that it was intended to take the same
parameters as netif_dbg() etc.  (Currently it is only used by the
sfc driver, in which I worked on that assumption.)

In commit a4ed89cb I changed the definition used when VERBOSE_DEBUG is
not defined, but I failed to notice that the definition used when
VERBOSE_DEBUG is defined was also not as I expected.  Change that to
match netif_dbg() as well.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>