PM / sleep: Make async suspend/resume of devices use device links

PM / sleep: Make async suspend/resume of devices use device links

Make the device suspend/resume part of the core system
suspend/resume code use device links to ensure that supplier
and consumer devices will be suspended and resumed in the right
order in case of async suspend/resume.

The idea, roughly, is to use dpm_wait() to wait for all consumers
before a supplier device suspend and to wait for all suppliers
before a consumer device resume.

Signed-off-by: Rafael J. Wysocki <[email protected]>
Tested-by: Marek Szyprowski <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>