CVE-2026-31605 fbdev: udlfb: avoid divide-by-zero on FBIOPUT_VSCREENINFO

In the Linux kernel, the following vulnerability has been resolved: fbdev: udlfb: avoid divide-by-zero on FBIOPUTVSCREENINFO Much like commit 19f953e74356 "fbdev: fbpm2fb: Avoid potential divide by zero error", we also need to prevent that same crash from happening in the udlfb driver as it uses...