I'd like to thank John Stul and others for helping
me along the way.

A lot of cleanups fell out of this.  For example, the get_compare()
tick_op was totally unused, so was deleted.  And the most often used
tick_op members were grouped together for cache-friendlyness.

The sparc64 TSC is given to the kernel as a one-shot timer.

tick_ops->init_timer() simply turns off the privileged bit in
the tick register (when possible), and disables the interrupt
by setting bit 63 in the compare register.  The ->disable_irq()
op also sets this bit.

tick_ops->add_compare() is changed to:

1) Add the given delta to "tick" not to "compare"
2) Return a boolean which, if true, means that the tick
   value read after writing the compare value was found
   to have incremented past the initial tick value.  This
   mirrors logic used in the HPET driver's ->next_event()
   method.

Each tick_ops implementation also now provides a name string.
And we feed this into the clocksource and clockevents layers.

Signed-off-by: David S. Miller <davem@davemloft.net>