erofs: clean up parsing of fscache related options

... to avoid the mess of conditional preprocessing as we are continually
adding fscache related mount options.

Reviewd-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230112065431.124926-3-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

fs/erofs/super.c

@@ -577,26 +577,25 @@ static int erofs_fc_parse_param(struct fs_context *fc,
 		}
 		++ctx->devs->extra_devices;
 		break;
-	case Opt_fsid:
 #ifdef CONFIG_EROFS_FS_ONDEMAND
+	case Opt_fsid:
 		kfree(ctx->fsid);
 		ctx->fsid = kstrdup(param->string, GFP_KERNEL);
 		if (!ctx->fsid)
 			return -ENOMEM;
-#else
-		errorfc(fc, "fsid option not supported");
-#endif
 		break;
 	case Opt_domain_id:
-#ifdef CONFIG_EROFS_FS_ONDEMAND
 		kfree(ctx->domain_id);
 		ctx->domain_id = kstrdup(param->string, GFP_KERNEL);
 		if (!ctx->domain_id)
 			return -ENOMEM;
+		break;
 #else
-		errorfc(fc, "domain_id option not supported");
-#endif
+	case Opt_fsid:
+	case Opt_domain_id:
+		errorfc(fc, "%s option not supported", erofs_fs_parameters[opt].name);
 		break;
+#endif
 	default:
 		return -ENOPARAM;
 	}