USB: fixup usb_hub_descriptor length name ...

All other descriptors have their length field named bLength, except
imported usb_hub_descriptor from Linux uses bDescLength. Adjust the
name to match the others.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

USB: reduce USB_MAXCHILDREN on imported ch11.h ...

Barebox supports up to 8 USB devices attached on a Hub, Linux does 31.
Reduce the USB_MAXCHILDREN define in ch11.h to the Barebox one and
put a comment above.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

USB: import ch11.h from Linux ...

Linux has an extra include for chapter 11 (Hub Specification) of USB 2.0
spec. We already have a ch9.h, so import the one from Linux.

Barebox specific changes will be patched up later.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>