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_aes.function b/tests/suites/test_suite_aes.function
index 9734aa0..8fe0bda 100644
--- a/tests/suites/test_suite_aes.function
+++ b/tests/suites/test_suite_aes.function
@@ -129,7 +129,7 @@
     dst = unhexify_alloc( hex_dst_string, &dst_len );
     TEST_ASSERT( src_len == dst_len );
 
-    output = zero_alloc( dst_len );
+    output = mbedtls_test_zero_alloc( dst_len );
 
     TEST_ASSERT( mbedtls_aes_xts_setkey_enc( &ctx, key, key_len * 8 ) == 0 );
     TEST_ASSERT( mbedtls_aes_crypt_xts( &ctx, MBEDTLS_AES_ENCRYPT, src_len,
@@ -172,7 +172,7 @@
     dst = unhexify_alloc( hex_dst_string, &dst_len );
     TEST_ASSERT( src_len == dst_len );
 
-    output = zero_alloc( dst_len );
+    output = mbedtls_test_zero_alloc( dst_len );
 
     TEST_ASSERT( mbedtls_aes_xts_setkey_dec( &ctx, key, key_len * 8 ) == 0 );
     TEST_ASSERT( mbedtls_aes_crypt_xts( &ctx, MBEDTLS_AES_DECRYPT, src_len,