USB Consolidate descriptor definitions

The header files usb.h and usbdescriptors.h have the same nameed
structure definitions for

usb_config_descriptor
usb_interface_descriptor
usb_endpoint_descriptor
usb_device_descriptor
usb_string_descriptor

These are out right duplicates in usb.h

usb_device_descriptor
usb_string_descriptor

This one has extra unused elements

usb_endpoint_descriptor

	unsigned char	bRefresh
	unsigned char	bSynchAddress;

These in usb.h have extra elements at the end of the usb 2.0
specified descriptor and are used.

usb_config_descriptor
usb_interface_descriptor

The change is to consolidate the definition of the descriptors
to usbdescriptors.h.  The dublicates in usb.h are removed.
The extra element structure will have their name shorted by
removing the '_descriptor' suffix.

So

usb_config_descriptor -> usb_config
usb_interface_descriptor -> usb_interface

For these, the common descriptor elements are accessed now
by an element 'desc'.

As an example

-	if (iface->bInterfaceClass != USB_CLASS_HUB)
+	if (iface->desc.bInterfaceClass != USB_CLASS_HUB)

This has been compile tested on MAKEALL arm, ppc and mips.

Signed-off-by: Tom Rix <Tom.Rix@windriver.com>