dmaengine: sirf: add CSRatlas7 SoC support

add support for new CSR atlas7 SoC. atlas7 exists V1 and V2 IP.
atlas7 DMAv1 is basically moved from marco, which has never been
delivered to customers and renamed in this patch.
atlas7 DMAv2 supports chain DMA by a chain table, this
patch also adds chain DMA support for atlas7.

atlas7 DMAv1 and DMAv2 co-exist in the same chip. there are some HW
configuration differences(register offset etc.) with old prima2 chips,
so we use compatible string to differentiate old prima2 and new atlas7,
then results in different set in HW for them.
Signed-off-by: Hao Liu <Hao.Liu@csr.com>
Signed-off-by: Yanchang Li <Yanchang.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

Documentation/devicetree/bindings/dma/sirfsoc-dma.txt

@@ -3,7 +3,8 @@
 See dma.txt first
 
 Required properties:
-- compatible: Should be "sirf,prima2-dmac" or "sirf,marco-dmac"
+- compatible: Should be "sirf,prima2-dmac", "sirf,atlas7-dmac" or
+  "sirf,atlas7-dmac-v2"
 - reg: Should contain DMA registers location and length.
 - interrupts: Should contain one interrupt shared by all channel
 - #dma-cells: must be <1>. used to represent the number of integer