refactor: use Bash expressions to generate boot arguments

This change removes the final remaining macro used by the LAVA job
template files, which is `BOOT_ARGUMENTS`. In its place, use a simple
Bash expression which loops over the boot arguments and generates the
boot argument array entries.

Signed-off-by: Chris Kay <chris.kay@arm.com>
Change-Id: I688c819179ed0a4dea48d23a222acb1c3ef55625
diff --git a/script/lava-templates/fvp-linux.yaml b/script/lava-templates/fvp-linux.yaml
index e871aff..96f69fe 100644
--- a/script/lava-templates/fvp-linux.yaml
+++ b/script/lava-templates/fvp-linux.yaml
@@ -70,4 +70,9 @@
     timeout:
       minutes: 30
     arguments:
-{BOOT_ARGUMENTS}
+
+$(for boot_argument in "${boot_arguments[@]:?}"; do
+	cat <<-YAML
+      - $(echo "${boot_argument}" | jq -R .)
+	YAML
+done)