lib/uuid: add a test module

It appears that somehow I missed a test of the latest UUID rework which
landed in the kernel.  Present a small test module to avoid such cases
in the future.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>