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/mpc8xx/fdt.c b/cpu/mpc8xx/fdt.c
index 567094a..7130983 100644
--- a/cpu/mpc8xx/fdt.c
+++ b/cpu/mpc8xx/fdt.c
@@ -40,7 +40,7 @@
 		gd->brg_clk, 1);
 
 	/* Fixup ethernet MAC addresses */
-	fdt_fixup_ethernet(blob, bd);
+	fdt_fixup_ethernet(blob);
 
 	fdt_fixup_memory(blob, (u64)bd->bi_memstart, (u64)bd->bi_memsize);
 }