dmaengine: DW DMAC: add multi-block property to device tree

Several versions of DW DMAC have multi block transfers hardware
support. Hardware support of multi block transfers is disabled
by default if we use DT to configure DMAC and software emulation
of multi block transfers used instead.
Add multi-block property, so it is possible to enable hardware
multi block transfers (if present) via DT.

Switch from per device is_nollp variable to multi_block array
to be able enable/disable multi block transfers separately per
channel.

Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

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

@@ -27,6 +27,8 @@ Optional properties:
   that services interrupts for this device
 - is_private: The device channels should be marked as private and not for by the
   general purpose DMA channel allocator. False if not passed.
+- multi-block: Multi block transfers supported by hardware. Array property with
+  one cell per channel. 0: not supported, 1 (default): supported.
 
 Example: