ARM: dts: gr8-evb: Fix RTC vendor

For some reason, the RTC vendor is reported to be phg, while the part is
actually made by the much more known NXP. Fix that.
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

arch/arm/boot/dts/sun5i-gr8-evb.dts

@@ -150,7 +150,7 @@ wm8978: codec@1a {
 	};
 
 	pcf8563: rtc@51 {
-		compatible = "phg,pcf8563";
+		compatible = "nxp,pcf8563";
 		reg = <0x51>;
 	};
 };