powerpc/4xx: Add missing USB and i2c devices to Canyonlands

This adds the device-tree entries for a handful of devices on the
Canyonlands board, such as the EHCI and OHCI controllers, the real
time clock and the AD7414 thermal monitor.

I also updated the defconfig to enable various options related to
these devices.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>