OHCI: make autostop conditional on CONFIG_PM

Unlike UHCI, OHCI does not exert any DMA load on the system when no
devices are connected.  Consequently there is no advantage to doing
an autostop other than the power savings, so we shouldn't compile the
necessary code unless CONFIG_PM is enabled.

This patch (as820) makes the root-hub suspend and resume routines
conditional on CONFIG_PM.  It also prevents autostop from activating
if the device_may_wakeup flag isn't set; some people use this flag to
alert the driver about Resume-Detect bugs in the hardware.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>