[PATCH] USB: move <linux/usb_cdc.h> to <linux/usb/cdc.h>

This moves <linux/usb_cdc.h> to <linux/usb/cdc.h> to reduce some of the
clutter of usb header files.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>