github: ci: Enable armhf

Since repo is public it may run for free in forks.

Signed-off-by: Philippe Coval <philippe.coval@silabs.com>

Author: rzr

.github/workflows/build-rootfs.yml

@@ -14,7 +14,7 @@ jobs:
         arch:
           - amd64
           - arm64
-          # - armhf # TODO Enable when supported
+          - armhf # TODO Enable when supported
     steps:
       - uses: actions/checkout@v4.1.1
         with: