netlink: Make nlmsg_find_attr take a const nlmsghdr*.
netlink: Make nlmsg_find_attr take a const nlmsghdr*.

This will let us use it on a nlmsghdr stored inside a netlink_callback.

Signed-off-by: Nelson Elhage <5189bc64eef7cb2f8e15afbc1a394127239e0cab@ksplice.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs