Merge branch 'bpf-allow-may_goto-0-instruction'

Yonghong Song says:

====================
Emil Tsalapatis from Meta reported such a case where 'may_goto 0' insn is
generated by clang-19 compiler and this caused verification failure
since 'may_goto 0' is rejected by verifier.

In fact, 'may_goto 0' insn is actually a no-op and it won't hurt
verification. The only side effect is that the verifier will convert
the insn to a sequence of codes like
   /* r10 - 8 stores the implicit loop count */
   r11 = *(u64 *)(r10 -8)
   if r11 == 0x0 goto pc+2
   r11 -= 1
   *(u64 *)(r10 -8) = r11

With this patch set 'may_goto 0' insns are allowed in verification which
also removes those insns.

Changelogs:
  v1 -> v2:
    - Instead of a separate function, removing 'may_goto 0' in existing
      func opt_remove_nops().
====================

Link: https://patch.msgid.link/20250118192019.2123689-1-yonghong.song@linux.dev


Signed-off-by: Alexei Starovoitov <ast@kernel.org>