Wip/martyn/u boot installer

apertis-installer-uboot.yaml

 {{ $architecture := or .architecture "armhf" }}
 {{ $target := or .target "mx6qsabrelite" }}
 {{ $mirror := or .mirror "https://repositories.apertis.org/apertis/" }}
-{{ $suite := or .suite "18.12" }}
+{{ $suite := or .suite "2019dev0" }}
 {{ $timestamp := or .timestamp "00000000.0" }}
 {{ $image := or .image (printf "apertis-%s-installer-%s-%s_%s" $suite $architecture $target $timestamp) }}
 
@@ -11,8 +11,7 @@ actions:
   - action: image-partition
     imagename: {{ $image }}.img
     imagesize: 300M
-    partitiontype: gpt
-    gpt_gap: {{ sector 6144 }}b
+    partitiontype: msdos
 
     mountpoints:
       - mountpoint: /