This patch splits up the usb structures to have two structs,
"usb_XXX_descriptor" with just the descriptor, and "usb_host_XXX" (or
something similar) to wrap it and add the "extra" pointers plus the
array of related descriptors that the host parsed during enumeration.
(2 or 3 words extra in each"usb_host_XXX".)  This further matches the
"on the wire" data and enables the gadget drivers to share the same
header file.

Covers all the linux/drivers/usb/* and linux/sound/usb/* stuff, but
not a handful of other drivers (bluetooth, iforce, hisax, irda) that
are out of the usb tree and will likely be affected.