ipv6: remove redundant assignment to variable err

The variable err is being initialized with a value that is never read and
it is being updated later with a new value. The initialization is redundant
and can be removed.  Also re-order variable declarations in reverse
Christmas tree ordering.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>