Revert "USB: Correct Makefile to make isp1760 buildable"

This reverts commit 26e12875.

A larger patch (f7e7aa58) a few days after this one added the same line
to the Makefile, but in a different place.  While it'd be more correct to
revert that one, it's easier to revert this one because this is a
one-liner.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
CC: Greg Kroah-Hartman <gregkh@suse.de>
CC: linux-usb@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>