USB: MUSB: upgrade the isochronous API

This patch attempts to fix the isochonour API in the musb host
driver.  In particular, the urb->start_frame field should always be
set by the driver; it isn't an input parameter.

The simplest way to accomplish this is to treat all URBs as though the
URB_ISO_ASAP flag was set.  This won't give the right behavior when an
underrun occurs, but I don't know enough about the musb driver to
handle that case.

Unfortunately, I have no way to test this change.

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