USB: isp116x: remove dependency on CONFIG_USB_DEBUG

Move all debugging messages in the driver to use the dynamic debug
subsystem, and not rely on CONFIG_USB_DEBUG to turn them on or off.

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

It also removes the pointless IRQ_TEST() macro, as that was totally
useless and obviously never used.

Cc: Olav Kongas <ok@artecdesign.ee>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>