ARM: dts: add Raspberry Pi Compute Module and IO board

The Raspberry Pi Compute Module (CM1) is a SoM which contains a
BCM2835 processor, 512 MB RAM and a 4 GB eMMC. There is also a carrier
board which is called Compute Module IO Board.

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