powerpc/4xx: Add Canyonlands suspend and idle support

- Add Clock Power Management (CPM) node to dts tree
- Add idle-doze entry in CPM node
- Add standby entry in CPM node
- Add PM and SUSPEND support by default in defconfig
- Remove UART2 and UART3 as they are unused, this will
  allow CPM to put unused-units (UART2 and UART3) to sleep.

Signed-off-by: Victor Gallardo <vgallardo@apm.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>