x86: provide delay loop for x86_64.

This is for consistency with i386. We call use_tsc_delay()
at tsc initialization for x86_64, so we'll be always using it.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/tsc.c

@@ -513,6 +513,7 @@ void __init tsc_init(void)
 	 */
 	for_each_possible_cpu(cpu)
 		set_cyc2ns_scale(cpu_khz, cpu);
+	use_tsc_delay();
 
 	if (tsc_disabled > 0)
 		return;