dmaengine: remove slave_id config field

All references to the slave_id field have been removed, so remove the
field as well to prevent new references from creeping in again.

Originally this allowed slave DMA drivers to configure which device
is accessed with the dmaengine_slave_config() call, but this was
inconsistent, as the same information is also passed while requesting
a channel, and never changes in practice.

In modern kernels, the device is always selected when requesting
the channel, so the .slave_id field is no longer useful.
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20211122222203.4103644-12-arnd@kernel.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

include/linux/dmaengine.h

@@ -418,9 +418,6 @@ enum dma_slave_buswidth {
  * @device_fc: Flow Controller Settings. Only valid for slave channels. Fill
  * with 'true' if peripheral should be flow controller. Direction will be
  * selected at Runtime.
- * @slave_id: Slave requester id. Only valid for slave channels. The dma
- * slave peripheral will have unique id as dma requester which need to be
- * pass as slave config.
  * @peripheral_config: peripheral configuration for programming peripheral
  * for dmaengine transfer
  * @peripheral_size: peripheral configuration buffer size
@@ -448,7 +445,6 @@ struct dma_slave_config {
 	u32 src_port_window_size;
 	u32 dst_port_window_size;
 	bool device_fc;
-	unsigned int slave_id;
 	void *peripheral_config;
 	size_t peripheral_size;
 };