dmaengine: at_hdmac: s/atc_get_bytes_left/atc_get_residue

Use dmaengine terminology and rename the method to better indicate what it
does: it gets the residue value which will be later on set with
dma_set_residue().

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20221025090306.297886-1-tudor.ambarus@microchip.com
Link: https://lore.kernel.org/r/20221025090306.297886-21-tudor.ambarus@microchip.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>