Add preemptirq instrumentation

Add preemptirq instrumentation

The tracepoints were introduced in kernl 4.15 alongside the config
option PREEMPTIRQ_EVENTS.

This enables tracing of disable and enable events for preemption and
irqs. For tracing preempt disable/enable events, DEBUG_PREEMPT must be
enabled. For tracing irq disable/enable events, PROVE_LOCKING must
be disabled.

See upstream commit:

  commit d59158162e032917a428704160a2063a02405ec6
  Author: Joel Fernandes <joelaf@google.com>
  Date:   Tue Oct 10 15:51:37 2017 -0700

    tracing: Add support for preempt and irq enable/disable events

    Preempt and irq trace events can be used for tracing the start and
    end of an atomic section which can be used by a trace viewer like
    systrace to graphically view the start and end of an atomic section and
    correlate them with latencies and scheduling issues.

    This also serves as a prelude to using synthetic events or probes to
    rewrite the preempt and irqsoff tracers, along with numerous benefits of
    using trace events features for these events.
Link: http://lkml.kernel.org/r/20171006005432.14244-3-joelaf@google.com
Link: http://lkml.kernel.org/r/20171010225137.17370-1-joelaf@google.com
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>