USB: sl811: remove CONFIG_USB_DEBUG dependency

This removes the dependency of the driver on CONFIG_USB_DEBUG and moves
it to us the dynamic debug subsystem instead.  Bonus is the fact that we
can now properly determine the exact hardware that is spitting out the
messages.

This lets debugging be enabled without having to rebuild the driver, an
important thing for users that can not do it.

Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>