Change to BSP sources

This allows sources of different kinds to be selected by the conditional

elements/bsp.bst

@@ -3,13 +3,14 @@ kind: junction
 
 ## This should be configuerable so that a option can be used to target diffrent bsps
 sources:
-- kind: git
-  (?):
+  - (?):
     - board == "pi3b":
+        kind: git
         url: https://gitlab.com/celduin/bsps/pi-3b-plus-bsp
         track: master
         ref: 744e8b694ed35869a0485ae457f057485a3b7ad4
     - board == "qemu":
+        kind: git
         url: https://gitlab.com/celduin/bsps/qemu-bsp
         track: master
         ref: 6e833797e4924ceec70dd3c3d4cb284c224b41db