libusb is now optional for libjaylink because support for TCP/IP
devices is always available.
Change-Id: I03f2566f8e1703276671ac0f353f72394d21f2f0
Signed-off-by: Marc Schink <openocd-dev@marcschink.de>
Reviewed-on: http://openocd.zylin.com/4204
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>