tools: process SVD files in parallel

This speeds up the generation of SVD files, for example as part of a
package build (where parallelism may not be desired, or tools should
auto-detect the number of threads to use).

.github/workflows/build-macos.yml

@@ -88,7 +88,7 @@ jobs:
         if: steps.cache-wasi-libc.outputs.cache-hit != 'true'
         run: make wasi-libc
       - name: make gen-device
-        run: make -j3 gen-device
+        run: make gen-device
       - name: Test TinyGo
         shell: bash
         run: make test GOTESTFLAGS="-short"