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: NElen Song <elen.song@atmel.com>
Signed-off-by: NLudovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>