tcl/board: add TI Tiva C ek-tm4c1294xl config

Change-Id: Iab070fe4c0f03ecc0db035b16dfb64105b0841be
Signed-off-by: Karl Palsson <karlp@tweak.net.au>
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-on: http://openocd.zylin.com/2063
Tested-by: jenkins