There is no reason to discard using source link local address when
remote netconsole IPv6 address is set to be link local one.

The patch allows administrators to use IPv6 netconsole without
explicitly configuring source address:

    netconsole=@/,@fe80::5054:ff:fe2f:6012/
Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>