wifitest Porting guide

Before porting wifitest, please make your code base built onece. It will make sure whether the build break is caused by wifitest or not.

1. Put the whole wifitest folder into external
2. mm the wifitest in external to generate new binary
3. run script porting.sh by wifi solution => ex. bash porting_bcm.sh / bash porting_intel.sh
4. the diff will be change into hardware/broadcom/wlan/wifitest
5. delete the whole wifitest folder in external
6. re-compile the system image again to check if porting is ok