DMA transfer to/from SRC

     DMA      DMApp
[MEM] -> [SRC] -> [SSIU] -> [SSI]

     DMA      DMApp
[MEM] <- [SRC] <- [SSIU] <- [SSI]

Current sound driver is supporting SSI/SRC random connection.
So, this patch is trying
SSI3 -> SRC3
SSI4 <- SRC4
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>