drivers/usb: regorganisation

move to linux usb driver organisation

as following

drivers/usb/gadget
drivers/usb/host
drivers/usb/musb

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Remy Bohmer <linux@bohmer.net>
diff --git a/drivers/serial/usbtty.c b/drivers/serial/usbtty.c
index d8b1387..f711d0b 100644
--- a/drivers/serial/usbtty.c
+++ b/drivers/serial/usbtty.c
@@ -94,7 +94,7 @@
  * Descriptors, Strings, Local variables.
  */
 
-/* defined and used by usbdcore_ep0.c */
+/* defined and used by gadget/ep0.c */
 extern struct usb_string_descriptor **usb_strings;
 
 /* Indicies, References */