Revert "ipv6: annotate some data-races around sk->sk_prot"

This reverts commit cb632144 which is
commit 086d4905 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I162811520b878e1eba080376f8deeb87f9b9ddac
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>