bpf: Fix stackmap overflow check in __bpf_get_stackid()

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix stackmap overflow check in __bpf_get_stackid() Syzkaller reported a KASAN slab-out-of-bounds write in __bpf_get_stackid() when copying stack trace data. The issue occurs when the perf trace contains more stack entries than the stack map bucket can hold, leading to an out-of-bounds write in the bucket's data array.