USB: Fix up terminology

USB is a HOST/DEVICE protocol, as per the specification and all
documentation.  Fix up terms that are not applicable to make things
match up with the terms used through the rest of the USB stack.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Felipe Balbi <balbi@kernel.org>
Link: https://lore.kernel.org/r/20200630174123.GA1906678@kroah.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/usb.c

@@ -19,9 +19,8 @@
  * just a collection of helper routines that implement the
  * generic USB things that the real drivers can use..
  *
- * Think of this as a "USB library" rather than anything else.
- * It should be considered a slave, with no callbacks. Callbacks
- * are evil.
+ * Think of this as a "USB library" rather than anything else,
+ * with no callbacks.  Callbacks are evil.
  */
 
 #include <linux/module.h>