Remove unused macro definition

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 1e579e9..985801b 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -902,7 +902,6 @@
                               int input_len,
                               int is_fail )
 {
-    #define MAX_LEN 64
     mbedtls_mpi_uint *X = NULL;
     mbedtls_mpi_uint *Y = NULL;
     mbedtls_mpi_uint *buff_m = NULL;