tests: Add mbedtls_test_ prefix to *hexify functions

Add mbedtls_test_ prefix to hexify() and unhexify()
test helper functions.

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

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/tests/suites/test_suite_cipher.function b/tests/suites/test_suite_cipher.function
index 02bf5f7..a399c70 100644
--- a/tests/suites/test_suite_cipher.function
+++ b/tests/suites/test_suite_cipher.function
@@ -1087,15 +1087,15 @@
     TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx,
                                        mbedtls_cipher_info_from_type( cipher_id ) ) );
 
-    key_len = unhexify( key, hex_key );
-    inputlen =  unhexify( input, hex_input );
-    resultlen = unhexify( result, hex_result );
+    key_len = mbedtls_test_unhexify( key, hex_key );
+    inputlen =  mbedtls_test_unhexify( input, hex_input );
+    resultlen = mbedtls_test_unhexify( result, hex_result );
 
     TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx, key, 8 * key_len, operation ) );
     if( MBEDTLS_MODE_CBC == ctx.cipher_info->mode )
         TEST_ASSERT( 0 == mbedtls_cipher_set_padding_mode( &ctx, MBEDTLS_PADDING_NONE ) );
 
-    iv_len = unhexify( iv, hex_iv );
+    iv_len = mbedtls_test_unhexify( iv, hex_iv );
 
     TEST_ASSERT( finish_result == mbedtls_cipher_crypt( &ctx, iv_len ? iv : NULL,
                                                         iv_len, input, inputlen,