fbdev: savage: Handle err return when savagefb_check_var failed

mainline inclusion
from mainline-v6.10-rc1
commit 6ad959b6703e2c4c5d7af03b4cfd5ff608036339
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAB0KC
CVE: CVE-2024-39475

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6ad959b6703e2c4c5d7af03b4cfd5ff608036339



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The commit 04e5eac8f3ab("fbdev: savage: Error out if pixclock equals zero")
checks the value of pixclock to avoid divide-by-zero error. However
the function savagefb_probe doesn't handle the error return of
savagefb_check_var. When pixclock is 0, it will cause divide-by-zero error.

Fixes: 04e5eac8f3ab ("fbdev: savage: Error out if pixclock equals zero")
Signed-off-by: Cai Xinchen <caixinchen1@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: He Yujie <coka.heyujie@huawei.com>