Btrfs: move fs/btrfs/ioctl.h to include/uapi/linux/btrfs.h

The header file will then be installed under /usr/include/linux so that
userspace applications can refer to Btrfs ioctls by name and use the same
structs used internally in the kernel.

Signed-off-by: Filipe Brandenburger <filbranden@google.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
diff --git a/include/linux/btrfs.h b/include/linux/btrfs.h
new file mode 100644
index 0000000..22d7991
--- /dev/null
+++ b/include/linux/btrfs.h
@@ -0,0 +1,6 @@
+#ifndef _LINUX_BTRFS_H
+#define _LINUX_BTRFS_H
+
+#include <uapi/linux/btrfs.h>
+
+#endif /* _LINUX_BTRFS_H */