fbdev: fbcon: select VT_HW_CONSOLE_BINDING

fbdev: fbcon: select VT_HW_CONSOLE_BINDING

fbdev provides framebuffer hotplugging, hence, we need to allow fbcon to
unbind from framebuffers. Unfortunately, fbcon_fb_unbind() cannot unbind
from the last framebuffer, unless console-unbinding is supported.

Fixing fbcon_unbind() to return 0 caused some horrible NULL-derefs in the
VT layer and I couldn't figure out why. Hence, lets just require
console-unbinding so fbdev hotplugging works with fbcon.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Link: http://lkml.kernel.org/r/1375445127-15480-9-git-send-email-dh.herrmann@gmail.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>