Fix compilation failure for ubuntu 3.13.0-36-generic (and above)

From 3.13.0-36, ubuntu did

while keeping the kernel version the same as 3.13.0-32. The only option
that was left then was to check for definition of skb_get_rxhash

Change-Id: Idd76936ee87904f37af17528dc9df88194fb2110
Closes Bug:1373574