USB: isp1362: remove _DBG() usage

If you want a debug call, just make it, so move to using the
already-there DBG() call.  No need to make things more complex than they
really need to be.

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