fbcon: Change fbcon_init from module_init to fs_initcall

Various fb drivers register themselves before module_init so as to have a
console as early as possible, this is of little use if fbcon does not
initialize early too.

Fbcon cannot initialize earlier then fs_initcall, because then the creation
of /sys/class/graphics/fbcon will fail.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>