dma: ste_dma40: Expand DT binding to accept 'high-priority channel' flag

This is used for MSP (audio) devices which is about to be fully DT:ed.

Cc: devicetree@vger.kernel.org
Acked-by: NVinod Koul <vinod.koul@intel.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/dma/ste-dma40.txt

@@ -50,6 +50,9 @@ Each dmas request consists of 4 cells:
         0x00000008: Use fixed channel:
                 Use automatic channel selection when unset
                 Use DMA request line number when set
+        0x00000010: Set channel as high priority:
+                Normal priority when unset
+                High priority when set
 
 Example: