[PATCH] x86_64: Support constantly ticking TSCs

On Intel Noconas the TSC ticks with a constant frequency.  Don't scale the
factor used by udelay when cpufreq changes the frequency.

This generalizes an earlier patch by Intel for this. 

Cc: <venkatesh.pallipadi@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>