CVE-2026-64088 batman-adv: tt: fix negative tt_buff_len

In the Linux kernel, the following vulnerability has been resolved: batman-adv: tt: fix negative ttbufflen batadvorignode::ttbufflen was declared as s16, but the field is never intended to hold a negative value. When a value greater than 32767 is assigned, it wraps to a negative signed integer. I...