Merge branch 'bugfix/dualcore_dport' into 'master'

component/esp32 : fix dualcore bug

1. When dual core cpu run access DPORT register, must do protection.
2. If access DPORT register, must use DPORT_REG_READ/DPORT_REG_WRITE and DPORT_XXX register operation macro.

See merge request !742

components/esp32/include/esp_dport_access.h

@@ -0,0 +1,22 @@
+// Copyright 2010-2017 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef _ESP_DPORT_ACCESS_H_
+#define _ESP_DPORT_ACCESS_H_
+
+void esp_dport_access_stall_other_cpu_start(void);
+void esp_dport_access_stall_other_cpu_end(void);
+void esp_dport_access_int_init(void);
+
+#endif /* _ESP_DPORT_ACCESS_H_ */