add AT32 to .travis.yml

.travis.yml

@@ -125,6 +125,8 @@ env:
   - RTT_BSP='fh8620' RTT_TOOL_CHAIN='sourcery-arm'
   - RTT_BSP='x1000' RTT_TOOL_CHAIN='sourcery-mips'
   - RTT_BSP='xplorer4330/M4' RTT_TOOL_CHAIN='sourcery-arm'
+  - RTT_BSP='at32/at32f403a-start' RTT_TOOL_CHAIN='sourcery-arm'
+  - RTT_BSP='at32/at32f407-start' RTT_TOOL_CHAIN='sourcery-arm'
 
 stage: compile
 script: