x86: cleanup CLI_STRING, STI_STRING and friends

Since the advent of ticket locking, CLI_STRING, STI_STRING, and friends
are not used anymore. They can now be safely deleted.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>