powerpc/44x: Add hwmon support to Sequoia device tree

This patch adds support for the AD7414 temperature sensor
on Sequoia PPC440EPx board.

Signed-off-by: Matthias Fuchs <matthias.fuchs@esd-electronics.com>
Acked-by: Stefan Roese <sr@denx.de>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>