arm64: dts: hisilicon: update compatible string for hikey960

Update compatible string for hikey960. HiKey960 is a develpment board built
with SoC Hi3660.
Signed-off-by: Guodong Xu <guodong.xu@linaro.org>
Signed-off-by: Chen Feng <puck.chen@hisilicon.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>

arch/arm64/boot/dts/hisilicon/hi3660-hikey960.dts

@@ -12,7 +12,7 @@
 
 / {
 	model = "HiKey960";
-	compatible = "hisilicon,hi3660";
+	compatible = "hisilicon,hi3660-hikey960", "hisilicon,hi3660";
 
 	aliases {
 		serial5 = &uart5;       /* console UART */