tests: Add mbedtls_test_ prefix to hexcmp()

Add mbedtls_test_ prefix to hexcmp() test helper
function.

Command to change *.function files:
find . -name "*.function" -exec awk -i inplace \
    '{sub(/hexcmp\>/,"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..0ec7d05 100644
--- a/tests/suites/test_suite_pkcs5.function
+++ b/tests/suites/test_suite_pkcs5.function
@@ -24,7 +24,7 @@
     TEST_ASSERT( mbedtls_pkcs5_pbkdf2_hmac( &ctx, pw_str->x, pw_str->len, salt_str->x, salt_str->len,
                                      it_cnt, key_len, key ) == 0 );
 
-    TEST_ASSERT( hexcmp( key, result_key_string->x, key_len, result_key_string->len ) == 0 );
+    TEST_ASSERT( mbedtls_test_hexcmp( key, result_key_string->x, key_len, result_key_string->len ) == 0 );
 
 exit:
     mbedtls_md_free( &ctx );