USB: Add macros for interrupt endpoint types.

The USB 3.0 spec defines a new way of differentiating interrupt
endpoints.  The idea is that some interrupt endpoints are used for
notifications, i.e. they continually NAK the transfer until something
changes on the device.  Other interrupt endpoints are used as a way to
periodically transfer data.

The USB 3.0 endpoint descriptor uses bits 5:4 of bmAttributes for
interrupt endpoints, to define the endpoint as either a Notification
endpoint, or a Periodic endpoint.  Introduce macros to dig out that
information.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>