Add ti-icdi support to opened

[hardwhack]

Add variant to openocd port to add support for ti-icdi (Tiva and Stellaris Launchpads). Proposed change is to add:

variant ti description {TI-ICDI interface on Stellaris Launchpad} {

configure.args-append --enable-ti-icdi depends_lib-append port:libusb

}

to the end of the port file. It does not add any more dependencies as afar as I can tell and builds cleanly on my system (10.9).