perf: Rework the PMU methods

Replace pmu::{enable,disable,start,stop,unthrottle} with
pmu::{add,del,start,stop}, all of which take a flags argument.

The new interface extends the capability to stop a counter while
keeping it scheduled on the PMU. We replace the throttled state with
the generic stopped state.

This also allows us to efficiently stop/start counters over certain
code paths (like IRQ handlers).

It also allows scheduling a counter without it starting, allowing for
a generic frozen state (useful for rotating stopped counters).

The stopped state is implemented in two different ways, depending on
how the architecture implemented the throttled state:

 1) We disable the counter:
    a) the pmu has per-counter enable bits, we flip that
    b) we program a NOP event, preserving the counter state

 2) We store the counter state and ignore all read/overflow events

Signed-off-by: Peter Zijlstra <[email protected]>
Cc: paulus <[email protected]>
Cc: stephane eranian <[email protected]>
Cc: Robert Richter <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: Lin Ming <[email protected]>
Cc: Yanmin <[email protected]>
Cc: Deng-Cheng Zhu <[email protected]>
Cc: David Miller <[email protected]>
Cc: Michael Cree <[email protected]>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <[email protected]>

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