psa_sim: improve log prints

- always print ERROR and FATAL messages because they should never
  occur, but when they do it's important to see them immediately;
- keep INFO prints under DEBUG guard;
- set client's PRINT as INFO message because otherwise it will
  mess test_suites's output;
- change some error messages from INFO to ERROR because that's
  what they are.

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/psa-client-server/psasim/include/util.h b/tests/psa-client-server/psasim/include/util.h
index 558149f..5eb8238 100644
--- a/tests/psa-client-server/psasim/include/util.h
+++ b/tests/psa-client-server/psasim/include/util.h
@@ -13,20 +13,18 @@
 #if defined(DEBUG)
 #define INFO(fmt, ...) \
     fprintf(stdout, "Info (%s - %d): " fmt "\n", __FILE__, __LINE__, ##__VA_ARGS__)
+#else /* !DEBUG */
+#define INFO(...)
+#endif /* DEBUG*/
 
 #define ERROR(fmt, ...) \
-    fprintf(stdout, "Error (%s - %d): " fmt "\n", __FILE__, __LINE__, ##__VA_ARGS__)
+    fprintf(stderr, "Error (%s - %d): " fmt "\n", __FILE__, __LINE__, ##__VA_ARGS__)
 
 #define FATAL(fmt, ...) \
     { \
-        fprintf(stdout, "Fatal (%s - %d): " fmt "\n", __FILE__, __LINE__, ##__VA_ARGS__); \
+        fprintf(stderr, "Fatal (%s - %d): " fmt "\n", __FILE__, __LINE__, ##__VA_ARGS__); \
         abort(); \
     }
-#else /* DEBUG */
-#define INFO(...)
-#define ERROR(...)
-#define FATAL(...)
-#endif /* DEBUG*/
 
 #define PROJECT_ID              'M'
 #define PATHNAMESIZE            256