x86: Move calibrate_cpu to tsc.c

Move the code where it's only user is. Also we need to look whether
this hardwired hackery might interfere with perfcounters.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/time.h

@@ -57,6 +57,4 @@ extern void time_init(void);
 
 #endif /* CONFIG_PARAVIRT */
 
-extern unsigned long __init calibrate_cpu(void);
-
 #endif /* _ASM_X86_TIME_H */