MI424WR - add rev D support

Add support for revision D of the MI424WR.
Rev D swaps LAN & WAN ports so this patch maintains
eth0 for LAN and eth1 for WAN. For details on rev D usage,
see http://wiki.openwrt.org/toh/actiontec/mi424wr



Signed-off-by: Jose Vasconcellos <jvasco@verizon.net>

SVN-Revision: 32820