[syzbot] [dri?] divide error in drm_mode_convert_to_umode

[syzbot]

syzbot has bisected this issue to:

commit ea40d7857d5250e5400f38c69ef9e17321e9c4a2
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Fri Oct 9 23:21:56 2020 +0000

    drm/vkms: fbdev emulation support

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14426df4180000
start commit:   445a555e0623 Add linux-next specific files for 20240209
git tree:       linux-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=16426df4180000
console output: https://syzkaller.appspot.com/x/log.txt?x=12426df4180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=85aa3388229f9ea9
dashboard link: https://syzkaller.appspot.com/bug?extid=0d7a3627fb6a42cf0863
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17d4bd48180000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=106ae642180000

Reported-by: syzbot+0d7a3627fb6a42cf0863 at syzkaller.appspotmail.com
Fixes: ea40d7857d52 ("drm/vkms: fbdev emulation support")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection