pitx-imx8m: set 1080p60 display timings

- Resolution 1920x1080 @60Hz seems to work stable on tested HDMI
  displays.
Signed-off-by: Thomas Schaefer <thomas.schaefer@kontron.com>

arch/arm/dts/pitx-imx8mq.dts

@@ -284,14 +284,14 @@
 		native-mode = <&timing1>;
 
 		timing1: timing1 {
-			clock-frequency = <74250000>;
-			hactive = <1280>;
-			vactive = <720>;
-			hfront-porch = <220>;
-			hback-porch = <110>;
-			hsync-len = <40>;
-			vback-porch = <5>;
-			vfront-porch = <20>;
+			clock-frequency = <148500000>;
+			hactive = <1920>;
+			vactive = <1080>;
+			hfront-porch = <88>;
+			hback-porch = <148>;
+			hsync-len = <44>;
+			vback-porch = <36>;
+			vfront-porch = <4>;
 			vsync-len = <5>;
 		};
 	};