arm64: dts: rockchip: rk3366: add dma-coherent for rga device

When import dma_buf to rga driver, dma_map_sg will always do
cpu cache sync, it cause low performance.

Actually we don't want to do cpu cache sync on this context,
So set rga device with dma-coherent to skip cpu cache sync.

Change-Id: Ie256db6a072481953befafb5b8003b9c1e713436
Signed-off-by: Mark Yao <mark.yao@rock-chips.com>

arch/arm64/boot/dts/rockchip/rk3366.dtsi

@@ -963,6 +963,7 @@
 		clocks = <&cru ACLK_RGA>, <&cru HCLK_RGA>, <&cru SCLK_RGA>;
 		clock-names = "aclk_rga", "hclk_rga", "clk_rga";
 		power-domains = <&power RK3366_PD_VIO>;
+		dma-coherent;
 		status = "disabled";
 	};