serial: at91: add tx dma support
serial: at91: add tx dma support

Request a slave dma channel for tx dma use. Tx dma will setup a single transfer,
when transfer complete, it will call atmel_complete_tx_dma to do finish stuff.

Signed-off-by: Elen Song <7b02f5298de50b2547d5a5710802de9ac29a4a72@atmel.com>
Signed-off-by: Ludovic Desroches <627575320a9526cb6c91021c9940202b0e84c416@atmel.com>
Signed-off-by: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@linuxfoundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs