Add dma support for lpuart. This function depend on DMA driver. You can turn on it by write both the dmas and dma-name properties in dts node. Signed-off-by: Yuan Yao <yao.yuan@freescale.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>