stm class: Use correct UUID APIs

It appears that the STM code didn't manage to accurately decypher the
delicate inner workings of an alternative thought process behind the
UUID API and directly called generate_random_uuid() that clearly needs
to be a static function in lib/uuid.c.

At the same time, said STM code is poking directly at the byte array
inside the uuid_t when it uses the UUID for its internal purposes.

Fix these two transgressions by using intended APIs instead.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
[ash: changed back to uuid_t and updated the commit message]
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Link: https://lore.kernel.org/r/20210415091555.88085-1-alexander.shishkin@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>