Actually make fs_path_config / fs_path_config_from_file private

No one outside of libcutils is using these structs and we don't want
to leak them as they are private.

Test: build
Change-Id: I1c95564a9843c9155a333334008cbff7c7ff1f51
diff --git a/libcutils/fs_config.h b/libcutils/fs_config.h
new file mode 100644
index 0000000..66ad48b
--- /dev/null
+++ b/libcutils/fs_config.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+// Binary format for the runtime <partition>/etc/fs_config_(dirs|files) filesystem override files.
+struct fs_path_config_from_file {
+    uint16_t len;
+    uint16_t mode;
+    uint16_t uid;
+    uint16_t gid;
+    uint64_t capabilities;
+    char prefix[];
+} __attribute__((__aligned__(sizeof(uint64_t))));
+
+struct fs_path_config {
+    unsigned mode;
+    unsigned uid;
+    unsigned gid;
+    uint64_t capabilities;
+    const char* prefix;
+};