switch all platform_bus device/driver registering to platform_driver/device_register ...

now register_driver and register_device are for bus only usage.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>

of: add devicetree probing support ...

This adds code to probe devices from a devicetree. Most helper
functions are directly imported from Linux.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>