firmware-utils/mktplinkfw: add support for TL-WA7510N

[juhosg: separated from the http://patchwork.openwrt.org/patch/2820/

 patch]

Signed-off-by: Stefan Helmert <helst_listen@aol.de>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

SVN-Revision: 34189