fbcon: fix situation where fbcon gets deinitialised and can't reinit.

fbcon: fix situation where fbcon gets deinitialised and can't reinit.

Situation as follow:
2 GPUs + vesafb + kms.

GPU 1 is primary, vesafb binds to it as fb0
radeon loads
GPU 0 loads as fb1
GPU 1 loads, vesafb gets kicked off which causes fb0 to unbind
console, which causes the dummy console to rebind.

this means fbcon_deinit gets called, which calls fbcon_exit
since the console isn't bound anymore and we set fbcon_has_exited.

GPU 1 creates a new fb0 which is primary and we want to be console.
fbcon_fb_registered gets called sets the primary up and calls set_con2fb_map,
however as fbcon_has_exited is set nothing further ever happens.

This patch bypasses the fbcon_has_exited and checks if the console is unbound,
if its unbound it calls the fbcon_takeover which calls the vt layer to
call the fbcon_startup method and everthing works.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>