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/include/fdt_support.h b/include/fdt_support.h
index a7c6326..f2f2cd5 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -45,7 +45,7 @@
 void do_fixup_by_compat_u32(void *fdt, const char *compat,
 			    const char *prop, u32 val, int create);
 int fdt_fixup_memory(void *blob, u64 start, u64 size);
-void fdt_fixup_ethernet(void *fdt, bd_t *bd);
+void fdt_fixup_ethernet(void *fdt);
 int fdt_find_and_setprop(void *fdt, const char *node, const char *prop,
 			 const void *val, int len, int create);
 void fdt_fixup_qe_firmware(void *fdt);