USB: EHCI: improvements to unlink_empty_async_suspended()

unlink_empty_async_suspended() is marked __maybe_unused.  This is
because its caller, ehci_bus_suspend(), is protected by "#ifdef
CONFIG_PM".  We should use the same protection here instead of
__maybe_unused.

unlink_empty_async_suspended() gets called only when the root hub is
suspended.  It's silly for it to call start_iaa_cycle() at such a
time; the IAA mechanism doesn't work when the root hub isn't running.
It should call end_unlink_async() instead.  But even this isn't
necessary, since there already is a call to end_iaa_cycle() right
before the call to unlink_empty_async_suspended().  All we have to do
is interchange the two subroutine calls.

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