external/iotivity: fix compilation warning
external/iotivity: fix compilation warning

The iotivity_simpleserver example is built by Makefile, not sconsscript
so that calling sconscript from iotivity is not needed.
This commit resolves shown below:
scons: warning: Ignoring missing SConscript '/home/sunghan/Work/TinyAra/TizenRT_forked/apps/examples/iotivity_simpleserver/SConscript'
File "/home/sunghan/Work/TinyAra/TizenRT_forked/external/iotivity/iotivity_1.2-rel/SConstruct", line 73, in <module>

JeonginKim/TizenRT,HONGCHAEHEE/TizenRT,jsdosa/TizenRT,jeongchanKim/TizenRT,sunghan-chang/TizenRT,JeonginKim/TizenRT,davidfather/TizenRT,Samsung/TizenRT,HONGCHAEHEE/TizenRT,an4967/TizenRT,HONGCHAEHEE/TizenRT,sunghan-chang/TizenRT,HONGCHAEHEE/TizenRT,jsdosa/TizenRT,Samsung/TizenRT,lokeshbv/TizenRT,jeongchanKim/TizenRT,jeongchanKim/TizenRT,btheosam/TizenRT,pillip8282/TizenRT,sunghan-chang/TizenRT,davidfather/TizenRT,jeongarmy/TizenRT,JeonginKim/TizenRT,an4967/TizenRT,HONGCHAEHEE/TizenRT,btheosam/TizenRT,chanijjani/TizenRT,chanijjani/TizenRT,jeongarmy/TizenRT,jeongchanKim/TizenRT,an4967/TizenRT,jeongarmy/TizenRT,chanijjani/TizenRT,pillip8282/TizenRT,chanijjani/TizenRT,jeongarmy/TizenRT,lokeshbv/TizenRT,jsdosa/TizenRT,pillip8282/TizenRT,pillip8282/TizenRT,chanijjani/TizenRT,btheosam/TizenRT,btheosam/TizenRT,lokeshbv/TizenRT,sunghan-chang/TizenRT,sunghan-chang/TizenRT,lokeshbv/TizenRT,lokeshbv/TizenRT,Samsung/TizenRT,pillip8282/TizenRT,davidfather/TizenRT,JeonginKim/TizenRT,JeonginKim/TizenRT,junmin-kim/TizenRT,jeongarmy/TizenRT,pillip8282/TizenRT,jeongchanKim/TizenRT,Samsung/TizenRT,jeongarmy/TizenRT,btheosam/TizenRT,lokeshbv/TizenRT,junmin-kim/TizenRT,an4967/TizenRT,jeongchanKim/TizenRT,junmin-kim/TizenRT,junmin-kim/TizenRT,Samsung/TizenRT,Samsung/TizenRT,davidfather/TizenRT,davidfather/TizenRT,chanijjani/TizenRT,sunghan-chang/TizenRT,jsdosa/TizenRT,jsdosa/TizenRT,davidfather/TizenRT,jsdosa/TizenRT,junmin-kim/TizenRT,junmin-kim/TizenRT,JeonginKim/TizenRT,an4967/TizenRT,jsdosa/TizenRT,btheosam/TizenRT,jeongchanKim/TizenRT,davidfather/TizenRT,sunghan-chang/TizenRT,an4967/TizenRT,jeongarmy/TizenRT,an4967/TizenRT,HONGCHAEHEE/TizenRT,junmin-kim/TizenRT,pillip8282/TizenRT,Samsung/TizenRT,chanijjani/TizenRT