linux-phytec-fsl

MLK-14543 tty: serial: fsl_lpuart: add lpuart32 dma support

The current driver don't support lpuart32 DMA mode.
The patch add lpuart32 tx/rx DMA support, there have two main changes:
- lpuart32 tx dma resue lpuart tx dma mode to reduce code duplication.
- lpuart32 rx dma still use prep_sg mode since imx7ulp don't support
  eeop mode that also ailgned with 4.1.y.

If don't use DMA mode, remove dma chan property in dts file.

Signed-off-by: Fugang Duan <fugang.duan@nxp.com>