fbdev: vesafb: bind to platform-framebuffer device

x86 creates platform-framebuffer platform devices for every system
framebuffer. Use these instead of creating a dummy device.

This requires us to remove the __init annotations as hotplugging may occur
during runtime.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Link: http://lkml.kernel.org/r/1375445127-15480-7-git-send-email-dh.herrmann@gmail.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>