lib: uuid: supporting building as part of host tools

Adjust the UUID library code so that it can be compiled as part of a
host tool.

This removes the one redundant log_debug() call, as well as the
incorrectly defined LOG_CATEGORY.

In general this is a fairly trivial change, just adjusting includes and
disabling list_guid.

This will be used by a new genguid tool to generate v5 GUIDs that match
those generated by U-Boot at runtime.

Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>