ip_tunnel: embed hash list head

The IP tunnel hash heads can be embedded in the per-net structure
since it is a fixed size. Reduce the size so that the total structure
fits in a page size. The original size was overly large, even NETDEV_HASHBITS
is only 8 bits!

Also, add some white space for readability.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Pravin B Shelar <pshelar@nicira.com&gt;.>
Signed-off-by: David S. Miller <davem@davemloft.net>