powerpc/8xxx: Add fdt_fixup_phy_connection helper

Add a common helper that will set the PHY connection type based on enum.
We use this on eTSEC, UCC, and will with Fman in the future.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/board/freescale/mpc8569mds/mpc8569mds.c b/board/freescale/mpc8569mds/mpc8569mds.c
index 795e565..743e712 100644
--- a/board/freescale/mpc8569mds/mpc8569mds.c
+++ b/board/freescale/mpc8569mds/mpc8569mds.c
@@ -622,8 +622,8 @@
 			break;
 		}
 
-		err = fdt_setprop_string(blob, nodeoff, "phy-connection-type",
-					"rmii");
+		err = fdt_fixup_phy_connection(blob, nodeoff, RMII);
+
 		if (err < 0) {
 			printf("WARNING: could not set phy-connection-type "
 				"%s.\n", fdt_strerror(err));