CI: add testing for edk2

For platforms that can do both u-boot and edk2, add a yml to switch from
u-boot to edk2.

Signed-off-by: Jon Mason <jon.mason@arm.com>

.gitlab-ci.yml

@@ -129,6 +129,7 @@ juno:
   parallel:
     matrix:
       - TOOLCHAINS: [gcc, clang]
+        FIRMWARE: [none, edk2]
 
 microbit-v1:
   extends: .build_and_test

ci/edk2.yml

@@ -0,0 +1,9 @@
+header:
+  version: 11
+
+local_conf_header:
+  bootfirmware: |
+    PREFERRED_PROVIDER_virtual/bootloader = "edk2-firmware"
+    MACHINE_FEATURES += "efi"
+    TFA_UBOOT = "0"
+    TFA_UEFI = "1"