libbpf: Drop redundant self-loop in emit_check_err

When the cleanup-label jump offset does not fit in s16, emit_check_err()
sets gen->error = -ERANGE and then emits a BPF_JMP_IMM(BPF_JA, 0, 0, -1)
self-loop.

The latter emit() is dead: gen->error is assigned on the preceding line,
and emit() then bails out early in realloc_insn_buf() the moment gen->error
is set, so the jump is never written into the instruction stream.

gen->error alone already marks the generation as failed. This is a follow-up
to 7dd6256 ("libbpf: fix off-by-one in emit_signature_match jump offset")
which removed the jump in emit_signature_match() but not in other locations.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260529094119.307264-1-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: borkmann

tools/lib/bpf/gen_loader.c

@@ -293,7 +293,6 @@ static void emit_check_err(struct bpf_gen *gen)
 		emit(gen, BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0, off));
 	} else {
 		gen->error = -ERANGE;
-		emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, -1));
 	}
 }