clock skew on B/W G3

[Rune Torgersen]

> From: George Anzinger [mailto:george at mvista.com] 
> But this is defined in include/asm/???.h  so you should be 
> able to set something more to your liking 
> (or rather to your archs liking).  It is true that it SHOULD 
> be defined as it is used to define 
> TICK_NSEC which is used to define the 
> jiffies<-->timeval/timespec conversions which would be VERY 
> slow it it were a variable.

Just make them variables, and compute them ONCE during boot.
ppc calls calibrate_decr() before enabling the timer interrupt anyways.

time_nsec is easy. 
in a platfrom specific file do (very simplified):

extern unsigned long time_nsec;

void platform_specific_calibrate_decr()
{
	time_nsec = REAL_TIME_NSEC;
}

This (of course) will do nothing about LATCH and ACTHZ that might be
used other places.