dmaengine: Add flow controller information to dma_slave_config
Flow controller is programmable for few controllers and there are few
intelligent peripherals like, Synopsys JPEG controller, that needs to be a flow
controller of DMA transfers on dest side.
For this, currently two drivers, pl08x and dw_dmac, support flow controller to
be passed from platform to these drivers.
Perhaps, this should be a part of struct dma_slave_config. This patch adds
another field device_fc to this structure. User drivers must pass this as true
if they want to be flow controller of certain transfers.