format: utilize the clang-format-ignore mechanism

Author: kurisaW

bsp/renesas/.clang-format-ignore

@@ -0,0 +1,11 @@
+# .clang-format-ignore File Description:
+# ----------------------------------------------------------------------------------------
+# 1. Used to specify which files or directories should be skipped by the clang-format tool.
+# 2. Follows syntax rules similar to .gitignore.
+# 3. Supports wildcard patterns and path matching.
+# 4. clang-format will recursively apply the .clang-format-ignore rules.
+
+# Renesas Vendor library
+**/ra/
+**/ra_cfg/
+**/ra_gen/