ir_sirc: minor Python and other nits

ir_sirc: minor Python and other nits

The .wait() wrapper always receives Python lists. There is only a single
IR pin (and its value isn't even used anywhere because appropriate edge
conditions get constructed). There is a delicate ss/es detail in the
.decode() routine concerning the IR frame's annotation's start. Don't
"continue" in the loop body's last statement, just "pass" and continue.