media: cedrus: skip invalid H.264 reference list entries

In the Linux kernel, the following vulnerability has been resolved: media: cedrus: skip invalid H.264 reference list entries Cedrus consumes H.264 ref_pic_list0/ref_pic_list1 entries from the stateless slice control and later uses their indices to look up decode->dpb[] in _cedrus_write_ref_list(). Rejecting such controls in cedrus_try_ctrl() would break existing userspace, since stateless H.264 reference lists may legitimately carry out-of-range indices for missing references. Instead, guard the actual DPB lookup in Cedrus and skip entries whose indices do not fit the fixed V4L2_H264_NUM_DPB_ENTRIES array. This keeps the fix local to the driver use site and avoids out-of-bounds reads from malformed or unsupported reference list entries.