vt: More locking checks

vt: More locking checks

I honestly have no idea what the subtle differences between
con_is_visible, con_is_fg (internal to vt.c) and con_is_bound are. But
it looks like both vc->vc_display_fg and con_driver_map are protected
by the console_lock, so probably better if we hold that when checking
this.

To do that I had to deinline the con_is_visible function.

Signed-off-by: Daniel Vetter <[email protected]>
Reviewed-by: Sam Ravnborg <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Maarten Lankhorst <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Nicolas Pitre <[email protected]>
Cc: Martin Hostettler <[email protected]>
Cc: Adam Borowski <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Mikulas Patocka <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]