Revert "video: fbdev: fbmem: fix pointer reference to null device field"

This reverts commit d6cd978f.
It has been solved differently already.

Signed-off-by: Helge Deller <deller@gmx.de>
Acked-by: Paul Menzel <pmenzel@molgen.mpg.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220210065824.368355-1-zhouzhouyi@gmail.com