[POWERPC] pasemi: Register i2c devices at boot

Setup i2c_board_info based on device tree contents.  This has to be
a device_initcall since we need PCI to be probed by the time we
run it, but before the actual driver is initialized.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>