While doing some cleanups of duplication #include entries,
I found what looks like a minor bug.

The keyspan driver does #include <linux/usb.h> twice. Not
normally a problem, because of the idempotent constructions.

But in this case the behaviour of the dbg() module depends on
the value of DEBUG. Keyspan tries to handle this, but the
first #include is before the definition, and the second one
has no effect. Patch attached.

I don't have the hardware to test, but it sure looks wrong now.