ARM: dts: use 'atmel' as at24 manufacturer in am335x-boneblue

Using 'at' as the <manufacturer> part of the compatible string is now
deprecated. Use a correct string: 'atmel,<model>'.
Signed-off-by: NBartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: NTony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am335x-boneblue.dts

@@ -342,7 +342,7 @@
 	};
 
 	baseboard_eeprom: baseboard_eeprom@50 {
-		compatible = "at,24c256";
+		compatible = "atmel,24c256";
 		reg = <0x50>;
 
 		#address-cells = <1>;