[AArch64][GISel] Silence warning caused by #130156

This caused build failures with -Werror
diff --git a/llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp b/llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
index dec3349..8d83fef 100644
--- a/llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
@@ -568,6 +568,7 @@
     default:
       break;
     }
+    break;
   default:
     break;
   }