perf: Optimize throttling code

By pre-computing the maximum number of samples per tick we can avoid a
multiplication and a conditional since MAX_INTERRUPTS >
max_samples_per_tick.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --cc include/linux/perf_event.h
Simple merge

diff --cc kernel/perf_event.c
Simple merge

diff --cc kernel/sysctl.c
Simple merge