Allow the linux command fw_setenv to set ethaddr.

There's a guard in the command fw_setenv to prevent you from changing
the mac address, probably to prevent you from shooting yourself in the
foot.  We'll take the safety off that because shooting ourselves in the
foot is what we do best.

Change-Id: I3cbc05974413f215ff18981115798c7f8563b653
diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index a46205d..5d3fcf2 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -375,12 +375,14 @@
 		/*
 		 * Ethernet Address and serial# can be set only once
 		 */
+#if 0
 		if ((strcmp (name, "ethaddr") == 0) ||
 			(strcmp (name, "serial#") == 0)) {
 			fprintf (stderr, "Can't overwrite \"%s\"\n", name);
 			errno = EROFS;
 			return -1;
 		}
+#endif
 
 		if (*++nxt == '\0') {
 			*env = '\0';