libbpf: fix off-by-one in emit_signature_match jump offset

libbpf: fix off-by-one in emit_signature_match jump offset

The offset for the cleanup-label jump is computed before the MOV R7
instruction is emitted, but the JMP lands after it. Account for the
extra insn in the offset calculation (-2 instead of -1). Drop the
redundant self-loop in the else branch; gen->error = -ERANGE already
marks the generation as failed.

Fixes: fb2b0e290147 ("libbpf: Update light skeleton for signing")
Signed-off-by: KP Singh <kpsingh@kernel.org>
Link: https://lore.kernel.org/r/20260522215337.662271-2-kpsingh@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>