atrace: Enable sched_waking if available

sched_waking helps to know when a wakeup happens at the earliest.
wakeups can originate on different CPUs which makes it impossible to
know just from sched_wakeup what the source was. Thankfully sched_waking
is just for that, enable it if its available.

Bug: 36415990

Change-Id: I489ca0112d5e0ed781888866a9efa57f17ca8a53
Signed-off-by: Joel Fernandes <joelaf@google.com>