[bsp] Add tm4c129x bsp building in travis-ci

.travis.yml

@@ -28,6 +28,7 @@ env:
   - RTT_BSP='lm3s8962' RTT_TOOL_CHAIN='sourcery-arm' 
   - RTT_BSP='lm3s9b9x' RTT_TOOL_CHAIN='sourcery-arm' 
   - RTT_BSP='lm4f232' RTT_TOOL_CHAIN='sourcery-arm' 
+  - RTT_BSP='tm4c129x' RTT_TOOL_CHAIN='sourcery-arm'
   - RTT_BSP='lpc176x' RTT_TOOL_CHAIN='sourcery-arm' 
   - RTT_BSP='lpc178x' RTT_TOOL_CHAIN='sourcery-arm' 
   - RTT_BSP='lpc2148' RTT_TOOL_CHAIN='sourcery-arm'