[PATCH] sysctl: x86_64: remove unnecessary use of insert_at_head

The only sysctl x86_64 provides are not provided elsewhere, so insert_at_head
is unnecessary.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>