USB: remove README file

This file is really really old, and doesn't make any sense to keep
around anymore, so just drop it.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/README

-To understand all the Linux-USB framework, you'll use these resources:
-
-    * This source code.  This is necessarily an evolving work, and
-      includes kerneldoc that should help you get a current overview.
-      ("make pdfdocs", and then look at "usb.pdf" for host side and
-      "gadget.pdf" for peripheral side.)  Also, Documentation/usb has
-      more information.
-
-    * The USB 2.0 specification (from www.usb.org), with supplements
-      such as those for USB OTG and the various device classes.
-      The USB specification has a good overview chapter, and USB
-      peripherals conform to the widely known "Chapter 9".
-
-    * Chip specifications for USB controllers.  Examples include
-      host controllers (on PCs, servers, and more); peripheral
-      controllers (in devices with Linux firmware, like printers or
-      cell phones); and hard-wired peripherals like Ethernet adapters.
-
-    * Specifications for other protocols implemented by USB peripheral
-      functions.  Some are vendor-specific; others are vendor-neutral
-      but just standardized outside of the www.usb.org team.
-
-Here is a list of what each subdirectory here is, and what is contained in
-them.
-
-core/		- This is for the core USB host code, including the
-		  usbfs files and the hub class driver ("hub_wq").
-
-host/		- This is for USB host controller drivers.  This
-		  includes UHCI, OHCI, EHCI, and others that might
-		  be used with more specialized "embedded" systems.
-
-gadget/		- This is for USB peripheral controller drivers and
-		  the various gadget drivers which talk to them.
-
-
-Individual USB driver directories.  A new driver should be added to the
-first subdirectory in the list below that it fits into.
-
-image/		- This is for still image drivers, like scanners or
-		  digital cameras.
-../input/	- This is for any driver that uses the input subsystem,
-		  like keyboard, mice, touchscreens, tablets, etc.
-../media/	- This is for multimedia drivers, like video cameras,
-		  radios, and any other drivers that talk to the v4l
-		  subsystem.
-../net/		- This is for network drivers.
-serial/		- This is for USB to serial drivers.
-storage/	- This is for USB mass-storage drivers.
-class/		- This is for all USB device drivers that do not fit
-		  into any of the above categories, and work for a range
-		  of USB Class specified devices. 
-misc/		- This is for all USB device drivers that do not fit
-		  into any of the above categories.