PM: Make PM_TRACE more architecture independent

PM: Make PM_TRACE more architecture independent

When trying to debug a suspend failure I started implementing
PM_TRACE for powerpc. I then noticed that I'm debugging a suspend
failure and so PM_TRACE isn't useful at all, but thought that
nonetheless this could be useful in the future.

Basically, to support PM_TRACE, you add a Kconfig option that
selects PM_TRACE and provides the infrastructure as per the
help text of PM_TRACE.

Signed-off-by: Johannes Berg <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>
Signed-off-by: Len Brown <[email protected]>