* [stm32] fix h7 uart V2 driver unused code.
* [DeviceDriver][serialv2] fix the serialv2 when using for console device on DMA mode.
* [stm32][art-pi] using serial v2 by default
* [DeviceDriver][SerialV2] Add termios for serial@V2 .
* [BSP][STM32] Add hardware flow control for STM32 serial@V2 driver.
* [DeviceDriver][Serial@V2] Add hardware flow control for serial V2.
* [stm32] fix h7 uart V2 driver unused code.
* [DeviceDriver][serialv2] fix the serialv2 when using for console device on DMA mode.
* [stm32][art-pi] using serial v2 by default