powerpc/44x: Add new compatible value for EMAC node of APM821XX dts file.

This compatible value will be used to distinguish some special features of APM821XX EMAC: no half duplex mode support, configuring jumbo frame.
Signed-off-by: Duc Dang <dhdang@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/powerpc/boot/dts/bluestone.dts

@@ -222,7 +222,7 @@ TAH0: emac-tah@ef601350 {
 
 			EMAC0: ethernet@ef600c00 {
 				device_type = "network";
-				compatible = "ibm,emac4sync";
+				compatible = "ibm,emac-apm821xx", "ibm,emac4sync";
 				interrupt-parent = <&EMAC0>;
 				interrupts = <0x0 0x1>;
 				#interrupt-cells = <1>;