Update to v5.12 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-5.12

Test: Boots flame device and runs bionic unit tests.
Test: Boots acloud device and runs bionic unit tests.

Change-Id: I8ac107ce9d4978be3ef9517b90ad6ecafd06785a
diff --git a/libc/kernel/uapi/linux/mount.h b/libc/kernel/uapi/linux/mount.h
index 99c2d98..5a112c9 100644
--- a/libc/kernel/uapi/linux/mount.h
+++ b/libc/kernel/uapi/linux/mount.h
@@ -18,6 +18,7 @@
  ****************************************************************************/
 #ifndef _UAPI_LINUX_MOUNT_H
 #define _UAPI_LINUX_MOUNT_H
+#include <linux/types.h>
 #define MS_RDONLY 1
 #define MS_NOSUID 2
 #define MS_NODEV 4
@@ -87,4 +88,12 @@
 #define MOUNT_ATTR_NOATIME 0x00000010
 #define MOUNT_ATTR_STRICTATIME 0x00000020
 #define MOUNT_ATTR_NODIRATIME 0x00000080
+#define MOUNT_ATTR_IDMAP 0x00100000
+struct mount_attr {
+  __u64 attr_set;
+  __u64 attr_clr;
+  __u64 propagation;
+  __u64 userns_fd;
+};
+#define MOUNT_ATTR_SIZE_VER0 32
 #endif