ARM: multi_v7_defconfig: Enable Broadcom Cygnus

Enable Broadcom Cygnus platform support in multi_v7_defconfig

Signed-off-by: Ray Jui <rjui@broadcom.com>
Signed-off-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>