CVE-2025-38312 fbdev: core: fbcvt: avoid division by 0 in fb_cvt_hperiod()

In the Linux kernel, the following vulnerability has been resolved: fbdev: core: fbcvt: avoid division by 0 in fbcvthperiod In fbfindmodecvt, iff mode-refresh somehow happens to be 0x80000000, cvt.frefresh will become 0 when multiplying it by 2 due to overflow. It's then passed to fbcvthperiod,...