USB: OHCI: Allow runtime PM without system sleep

Since ohci-hcd supports runtime PM, the .pm field in its pci_driver
structure should be protected by CONFIG_PM rather than
CONFIG_PM_SLEEP.

Without this change, OHCI controllers won't do runtime suspend if
system suspend or hibernation isn't enabled.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
cc: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>