lib: uuid: do not support UUID_v5 on TF-M platforms

When TF-M is enabled, Mbed TLS's MD module (which is used to generate
v5 UUIDs) will dispacth hash operations to TF-M. Unfortunately TF-M
does not support SHA-1 (because it's a weak algorithm) so the
computation will fail.

Signed-off-by: Valerio Setti <vsetti@baylibre.com>