fbcon: Remove obsolete reference to initmem_freed

initmem_freed was removed in v2.1.124, and the underlying issue was
fixed for good in commit 92b004d1 ("video/logo: prevent use of
logos after they have been freed").

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/b8b9147a48e233fe32e072f2085c7b413cd92a00.1654702835.git.geert+renesas@glider.be