ARM: multi_v7: add HREFv60 to multi_v7 defconfig

This is just a standard board for the Ux500, include it in the
v7 multiplatform defconfig.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>