tests: Add mbedtls_test_ prefix to zero_alloc()

Add mbedtls_test_ prefix to zero_alloc() test helper
function.

Command to change *.function files:
find . -name "*.function" -exec awk -i inplace \
    '{sub(/zero_alloc/,"mbedtls_test_&")}1' {} \;

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/tests/suites/test_suite_pkcs5.function b/tests/suites/test_suite_pkcs5.function
index 26f1d33..ee894f1 100644
--- a/tests/suites/test_suite_pkcs5.function
+++ b/tests/suites/test_suite_pkcs5.function
@@ -43,7 +43,7 @@
     params.p = params_hex->x;
     params.len = params_hex->len;
 
-    my_out = zero_alloc( ref_out->len );
+    my_out = mbedtls_test_zero_alloc( ref_out->len );
 
     my_ret = mbedtls_pkcs5_pbes2( &params, MBEDTLS_PKCS5_DECRYPT,
                           pw->x, pw->len, data->x, data->len, my_out );