PCI: fix incorrect error return in pci_enable_wake

This patch (as1186) fixes a minor mistake in pci_enable_wake().  When
the routine is asked to disable remote wakeup, it should not return an
error merely because the device is not allowed to do wakeups!

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>