BACKPORT: PM / wakeup: Show wakeup sources stats in sysfs

Add an ID and a device pointer to 'struct wakeup_source'. Use them to to
expose wakeup sources statistics in sysfs under
/sys/class/wakeup/wakeup<ID>/*.

Co-developed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Co-developed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Tri Vo <trong@android.com>
Tested-by: Kalesh Singh <kaleshsingh@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit c8377adfa78103be5380200eb9dab764d7ca890e)
[ Replaced ida_alloc()/ida_free( with) ida_simple_get()/ida_simple_remove() as
  the former is not present in 4.14. ]
Bug: 129087298
Signed-off-by: Tri Vo <trong@google.com>
Change-Id: Iecd3412423f9d499981f44d3b69507eaa62a2cd9