simplefb: Change simplefb_init from module_init to fs_initcall

One of the reasons for having the simplefb nodes in /chosen, and doing
explicit enumeration of the nodes there, is too allow enumerating them sooner,
so that we get a console earlier on.

Doing this earlier then fs_initcall is not useful, since the fb only turns
into a console when fbcon intializes, which is a fs_initcall too.

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