Merge branch 'driver_merge_tmp/merge_uart' into 'master'

Add UART driver

1. add uart.h and uart.c
2. add ESP_ERR_TIMEOUT in esp_err.h
3. add UART AHB FIFO address in uart_reg.h
4. modify xRingbufferSendFromISR return value in ringbuffer.c
5. add #include "soc/gpio_sig_map.h" in gpio.h

See merge request !146