usb: core: allow zero packet flag for interrupt urbs

Section 4.4.7.2 "Interrupt Transfer Bandwidth Requirements" of the USB3.0 spec
says:
	A zero-length data payload is a valid transfer and may be useful for
	some implementations.

So, extend the logic of allowing URB_ZERO_PACKET to interrupt urbs too.
Otherwise, the kernel throws warning of BOGUS transfer flags.

Signed-off-by: Amit Virdi <amit.virdi@st.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/urb.c

@@ -454,6 +454,7 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
 			URB_FREE_BUFFER);
 	switch (xfertype) {
 	case USB_ENDPOINT_XFER_BULK:
+	case USB_ENDPOINT_XFER_INT:
 		if (is_out)
 			allowed |= URB_ZERO_PACKET;
 		/* FALLTHROUGH */