[PATCH] powerpc: add of_get_mac_address() and update fsl_soc.c to use it

[Benjamin Herrenschmidt]

> +	return get_property(np, "address", NULL);

Since there is so much room for confusion with "address", please at
least do some basic sanity checking, like check that it's size is 6
bytes and maybe that the multicast bit isn't set.

Ben.