Fix GCC format-signedness warnings

Signed-off-by: Kenneth Soerensen <knnthsrnsn@gmail.com>
diff --git a/programs/psa/key_ladder_demo.c b/programs/psa/key_ladder_demo.c
index f492e0e..1dbbc81 100644
--- a/programs/psa/key_ladder_demo.c
+++ b/programs/psa/key_ladder_demo.c
@@ -101,7 +101,7 @@
         status = ( expr );                                      \
         if( status != PSA_SUCCESS )                             \
         {                                                       \
-            printf( "Error %d at line %u: %s\n",                \
+            printf( "Error %d at line %d: %s\n",                \
                     (int) status,                               \
                     __LINE__,                                   \
                     #expr );                                    \