ipv6: Various cleanups in route.c

1) x == NULL --> !x
2) x != NULL --> x
3) (x&BIT) --> (x & BIT)
4) (BIT1|BIT2) --> (BIT1 | BIT2)
5) proper argument and struct member alignment
Signed-off-by: David S. Miller <davem@davemloft.net>