It would fail the compile due to the newly added error checking testing
a bad macro for a "return value" unless USB_GADGET_DEBUG_FILES was
enabled.

Pointed out by Stephen Hemminger.
Acked-by: NStephen Hemminger <shemminger@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>