rtla: Use standard exit codes for result enum

rtla: Use standard exit codes for result enum

The result enum defines custom values for PASSED, ERROR, and FAILED.
These values correspond to standard exit codes EXIT_SUCCESS and
EXIT_FAILURE.

Update the enum to use the standard macros EXIT_SUCCESS and
EXIT_FAILURE to improve readability and adherence to standard C
practices.

The FAILED value is implicitly assigned EXIT_FAILURE + 1, so there
is no need to assign an explicit value.

Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Link: https://lore.kernel.org/r/20260106133655.249887-9-wander@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>