Also found a race condition between timer_disable and redraw, which
would happen if I debugger-paused inside common_hal_rgbmatrix_timer_disable
or put a delay or print inside it. That's what pausing inside reconstruct
fixes.
So that the "right timer" can be chosen, `timer_allocate` now gets the `self`
pointer. It's guaranteed at this point that the pin information is accurate,
so you can e.g., find a PWM unit related to the pins themselves.
This required touching each port to add the parameter even though it's
unused everywhere but raspberrypi.
