USB: usbatm: don't rely on CONFIG_USB_DEBUG

Enable the USB atm drivers to use the dynamic debugging subsystem, and
not rely on if CONFIG_USB_DEBUG is enabled or not for debugging
messages. This also provides a saner debug message, pointing out the
exact device the message is coming from.

This also means the drivers do not have to be rebuilt to get debugging
messages, important for getting information from users who can not
rebuild their kernels.

Cc: Duncan Sands <duncan.sands@free.fr>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>