USB: ohci-hub: Mark ohci_finish_controller_resume() as __maybe_unused

ohci_finish_controller_resume() is intended to be used in platform specific
drivers ohci-*.c, included from ohci-hcd.c. Some of them don't actually use
ohci_finish_controller_resume(), so mark it as __maybe_unused.

Signed-off-by: Roland Stigge <stigge@antcom.de>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>