fdt: rework fdt_fixup_ethernet() to use env instead of bd_t

Move to using the environment variables 'ethaddr', 'eth1addr', etc..
instead of bd->bi_enetaddr, bi_enet1addr, etc.

This makes the code a bit more flexible to the number of ethernet
interfaces.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/cpu/mpc85xx/fdt.c b/cpu/mpc85xx/fdt.c
index c159934..bc1550d 100644
--- a/cpu/mpc85xx/fdt.c
+++ b/cpu/mpc85xx/fdt.c
@@ -212,7 +212,7 @@
 
 #if defined(CONFIG_HAS_ETH0) || defined(CONFIG_HAS_ETH1) ||\
     defined(CONFIG_HAS_ETH2) || defined(CONFIG_HAS_ETH3)
-	fdt_fixup_ethernet(blob, bd);
+	fdt_fixup_ethernet(blob);
 #endif
 
 	do_fixup_by_prop_u32(blob, "device_type", "cpu", 4,