dt/bindings: arm-pl330: add description of arm, pl330-broken-no-flushp

This patch adds the "arm, pl330-broken-no-flushp" for arm-pl330.
Reviewed-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

Documentation/devicetree/bindings/dma/arm-pl330.txt

@@ -15,6 +15,7 @@ Optional properties:
     cells in the dmas property of client device.
   - dma-channels: contains the total number of DMA channels supported by the DMAC
   - dma-requests: contains the total number of DMA requests supported by the DMAC
+  - arm,pl330-broken-no-flushp: quirk for avoiding to execute DMAFLUSHP
 
 Example: