ARM: dts: cygnus: enable GPIO based hook detection

This enables GPIO based phone hook detection for Broadcom BCM911360
phone factor board (bcm911360_entphn)

Signed-off-by: Ray Jui <rjui@broadcom.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>