ipv6: Various cleanups in ip6_route.c

1) x == NULL --> !x
2) x != NULL --> x
3) if() --> if ()
4) while() --> while ()
5) (x & BIT) == 0 --> !(x & BIT)
6) (x&BIT) --> (x & BIT)
7) x=y --> x = y
8) (BIT1|BIT2) --> (BIT1 | BIT2)
9) if ((x & BIT)) --> if (x & BIT)
10) proper argument and struct member alignment

Signed-off-by: David S. Miller <davem@davemloft.net>