CVE-2026-89882 media: rkvdec: hevc: guard INTER_REF_PIC_SET_PRED index underflow

In the Linux kernel, the following vulnerability has been resolved: media: rkvdec: hevc: guard INTERREFPICSETPRED index underflow strefpicsetprediction computes the reference RPS index as strpsidx - deltaidxminus1 + 1 per HEVC spec equation 7-59. Both operands are u8, so when deltaidxminus1 + 1...