mesa: Add missing switch break in invalidate_framebuffer_storage()

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70411
Cc: "9.2" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/main/fbobject.c

@@ -3585,6 +3585,7 @@ invalidate_framebuffer_storage(GLenum target, GLsizei numAttachments,
                            "%s(attachment >= max. color attachments)", name);
                return;
             }
+            break;
          }
          default:
             goto invalid_enum;