fbmon: prevent division by zero in fb_videomode_from_videomode()

stable inclusion
from stable-v4.19.312
commit 1fb52bc1de55e9e0bdf71fe078efd4da0889710f
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9QGIW
CVE: CVE-2024-35922

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1fb52bc1de55e9e0bdf71fe078efd4da0889710f



---------------------------

[ Upstream commit c2d953276b8b27459baed1277a4fdd5dd9bd4126 ]

The expression htotal * vtotal can have a zero value on
overflow. It is necessary to prevent division by zero like in
fb_var_to_videomode().

Found by Linux Verification Center (linuxtesting.org) with Svace.

Signed-off-by: Roman Smirnov <r.smirnov@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Hui Tang <tanghui20@huawei.com>