video: fbdev: controlfb: remove obsolete module support

CONFIG_FB_CONTROL is bool, hence the Apple "control" frame buffer
driver cannot be built as a module.

Replace module_init() by device_initcall().

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200324134508.25120-4-b.zolnierkie@samsung.com