[PATCH v3 0/2] serial: fsl_lpuart: add DMA support

[Yuan Yao]

Changed in v3:
- Use the streaming DMA API for receive.
- Add the macro(SERIAL_FSL_LPUART_DMA) and dts node propertie for whether using the dma.
- Adjust some coding style.

Changed in v2:
- Add eDMA support for lpuart receive.
- Use dma_mapping_error test dma_map_single.
- Change some names of variable.
- Fix some bugs.
 
 Added in v1:
 - Add device tree bindings for lupart eDMA support.
 - Add eDMA support for lpuart send.