clockevents: Remove CONFIG_GENERIC_CLOCKEVENTS_BUILD

This option was for simpler migration to the clock events code.
Most architectures have been converted and the option has been
disfunctional as a standalone option for quite some time. Remove
it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5021859.jl9OC1medj@vostro.rjw.lan


Signed-off-by: Ingo Molnar <mingo@kernel.org>