boards: cc3235sf_launchxl: use OpenOCD from Zephyr SDK

We should use OpenOCD from the latest Zephyr SDK as opposed to using TI
OpenOCD.

There is a known issue with the current release (0.10.2) of the SDK in
how it resets the network processor, but we can deal with it
subsequently.

Signed-off-by: Vincent Wan <vincent.wan@linaro.org>