ci: Skip LFS, submodules for building toolchain

Signed-off-by: Tim Crawford <tcrawford@system76.com>

.github/workflows/ci.yaml

@@ -21,11 +21,12 @@ jobs:
     steps:
     - uses: actions/checkout@v4
       with:
-        lfs: true
-        submodules: recursive
-        fetch-tags: true
+        filter: tree:0
         fetch-depth: 0
 
+    - name: Checkout coreboot
+      run: git submodule update --init --checkout --force coreboot
+
     - name: Check coreboot toolchain exists
       id: get_coreboot_toolchain
       uses: actions/cache@v4