ARM: dts: bcm2837: Add missing GPIOs of Expander

After commit a98d90e7 ("gpio: raspberrypi-exp: Driver for RPi3 GPIO
expander via mailbox service") we are able to control the rest of the
GPIOs of the RPi 3. So add all the missing parts (ACT LED,
Wifi & BT control, HDMI detect) to the DT.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Eric Anholt <eric@anholt.net>