uuid: remove uuid_be defintions from the uapi header

We don't use uuid_be and the UUID_BE constants in any uapi headers, so make
them private to the kernel.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>