MPI random test: fix small-range test stats check when min > 1

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 1709677..a2d312f 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -1518,7 +1518,7 @@
 
     if( full_stats )
     {
-        for( b = 1; b < stats_len; b++ )
+        for( b = min; b < stats_len; b++ )
         {
             mbedtls_test_set_step( 1000000 + b );
             /* Assert that each value has been reached at least once.