Use BBR ACS main branch

Author: chetan-rathore

SystemReady-band/build-scripts/get_source.sh

@@ -168,9 +168,7 @@ get_linux-acs_src()
 get_bbr_acs_src()
 {
     echo "Downloading Arm BBR source code."
-    #git clone https://github.com/ARM-software/bbr-acs.git bbr-acs
-    ##TODO revert back to main branch
-    git clone --branch SR_execution_enviroment https://github.com/ARM-software/bbr-acs.git bbr-acs
+    git clone https://github.com/ARM-software/bbr-acs.git bbr-acs
     if [ -n "$ARM_BBR_TAG" ]; then
         # TAG provided.
         echo "Checking out Arm BBR TAG: $ARM_BBR_TAG"