Rename MPI-legacy test function for clarity

A mod version of the function will be added very soon.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/test_suite_bignum_random.function b/tests/suites/test_suite_bignum_random.function
index 184de5a..2250e8c 100644
--- a/tests/suites/test_suite_bignum_random.function
+++ b/tests/suites/test_suite_bignum_random.function
@@ -110,7 +110,7 @@
 /* END_CASE */
 
 /* BEGIN_CASE */
-void mpi_random_values( int min, char *max_hex )
+void mpi_legacy_random_values( int min, char *max_hex )
 {
     /* Same RNG as in mpi_core_random_basic */
     mbedtls_test_rnd_pseudo_info rnd_core = rnd_pseudo_seed;