[POWERPC] add of_get_mac_address and update fsl_soc.c to use it

Add function of_get_mac_address(), which obtains the best MAC address to use
from the device tree by checking various properties in order.  The order is:
'mac-address', then 'local-mac-address', then 'address'.  It skips properties
that contain invalid MAC addresses, which were probably not initialized
by U-Boot.

Update gfar_of_init() and fs_enet_of_init() in fsl_soc.c to call
of_get_mac_address().

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/sysdev/fsl_soc.c b/arch/powerpc/sysdev/fsl_soc.c
index 34161bc..d20f0292 100644
--- a/arch/powerpc/sysdev/fsl_soc.c
+++ b/arch/powerpc/sysdev/fsl_soc.c
@@ -233,14 +233,7 @@
 			goto err;
 		}
 
-		mac_addr = get_property(np, "local-mac-address", NULL);
-		if (mac_addr == NULL)
-			mac_addr = get_property(np, "mac-address", NULL);
-		if (mac_addr == NULL) {
-			/* Obsolete */
-			mac_addr = get_property(np, "address", NULL);
-		}
-
+		mac_addr = of_get_mac_address(np);
 		if (mac_addr)
 			memcpy(gfar_data.mac_addr, mac_addr, 6);
 
@@ -646,8 +639,9 @@
 			goto unreg;
 		}
 
-		mac_addr = get_property(np, "mac-address", NULL);
-		memcpy(fs_enet_data.macaddr, mac_addr, 6);
+		mac_addr = of_get_mac_address(np);
+		if (mac_addr)
+			memcpy(fs_enet_data.macaddr, mac_addr, 6);
 
 		ph = get_property(np, "phy-handle", NULL);
 		phy = of_find_node_by_phandle(*ph);
@@ -931,8 +925,9 @@
 			goto err;
 		r[0].name = enet_regs;
 
-		mac_addr = (void *)get_property(np, "mac-address", NULL);
-		memcpy(fs_enet_data.macaddr, mac_addr, 6);
+		mac_addr = of_get_mac_address(np);
+		if (mac_addr)
+			memcpy(fs_enet_data.macaddr, mac_addr, 6);
 
 		ph = (phandle *) get_property(np, "phy-handle", NULL);
 		if (ph != NULL)