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>

sandbox: add sdl video support ...

This will allow speed up the dev on framebuffer.

By default the resolution is VGA but this can be changed via cmdline.

We use a pthread to Flip the screen every 100ms as we can not detect when
barebox update it as barebox simpliy write in a buffer.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>