x86/timers: Move the simple udelay calibration to tsc.h

x86/timers: Move the simple udelay calibration to tsc.h

Commit dd759d93f4dd ("x86/timers: Add simple udelay calibration") adds
an static function in x86 boot-time initializations.

But, this function is actually related to TSC, so it should be maintained
in tsc.c, not in setup.c.

Move simple_udelay_calibration() from setup.c to tsc.c and rename it to
tsc_early_delay_calibrate for more readability.

Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1500003247-17368-1-git-send-email-douly.fnst@cn.fujitsu.com