PM: Prevent runtime suspend during system resume

This patch (as1591) moves the pm_runtime_get_noresume() and
pm_runtime_put_sync() calls from __device_suspend() and
device_resume() to device_prepare() and device_complete() in the PM
core.

The reason for doing this is to make sure that parent devices remain
at full power (i.e., don't go into runtime suspend) while their
children are being resumed from a system sleep.

The PCI core already contained equivalent code to serve the same
purpose.  The patch removes the duplicated code, since it is no longer
needed.  One of the comments from the PCI core gets moved into the PM
core, and a second comment is added to explain whe the _get_noresume
and _put_sync calls are present.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
PM: Allow runtime suspend again if prepare is failed

commit 8a5bdaf3 never allow the runtime suspend if prepare is failed.
The complete phase is invoked when calling __device_suspend.
It allows the runtime suspend again. But if prepare is failed,
__device_suspend won't be called and the complete phase won't also
called. Thus this runtime suspend will be blocked forever.

If prepare is failed, you should allow the runtime suspend again.

Change-Id: I57c7c04609299244a042f2524e1c65dbbdd91ae3