fbcon: delete delayed loading code

Before

commit 6104c370
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue Aug 1 17:32:07 2017 +0200

    fbcon: Make fbcon a built-time depency for fbdev

it was possible to load fbcon and fbdev drivers in any order, which
means that fbcon init had to handle the case where fbdev drivers where
already registered.

This is no longer possible, hence delete that code.

Note that the exit case is a bit more complex and will be done in a
separate patch.

Since I had to audit the entire fbcon load code I also spotted a wrong
function name in a comment in fbcon_startup(), which this patch also
fixes.

v2: Explain why we also fix the comment (Sam)

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Claudio Suarez <cssk@net-c.es>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Du Cheng <ducheng2@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220405210335.3434130-5-daniel.vetter@ffwll.ch