dmaengine: sa11x0: add DMA filters

Add DMA filters for the sa11x0 DMA channels.  This will allow us to
migrate away from directly using the DMA filter function in drivers.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>