dmaengine: Add device_terminate_all callback

Split out the terminate_all command from device_control to a dma_device
callback. In order to preserve backward capability, still rely on
device_control if no such callback has been implemented.

Eventually, this will allow to create a generic dma_slave_caps callback.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>