kas: corstone1000: set branch to scarthgap

The default branch will be scarthgap so the poky and
openembedded will follow this branch.

Signed-off-by: Bence Balogh <bence.balogh@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

kas/corstone1000-base.yml

@@ -5,7 +5,7 @@ distro: poky
 
 defaults:
   repos:
-    branch: master
+    branch: scarthgap
 
 repos:
   meta-arm: