Use the new endpoint helpers to lookup the interrupt-in endpoint,
and only print the corresponding debugging information in case it is
found.

Note that the descriptors are searched in reverse order to avoid any
regressions.
Signed-off-by: NJohan Hovold <johan@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>