decodetree: Remove "insn" argument from trans_* expanders

decodetree: Remove "insn" argument from trans_* expanders

This allows trans_* expanders to be shared between decoders
for 32 and 16-bit insns, by not tying the expander to the
size of the insn that produced it.

This change requires adjusting the two existing users to match.

Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>