Request for additional operator support for etl::io_port_*

[JoeBenczarski]

It would be a nice feature to be able to use |= and &= on etl::io_port_* types when relevant.

Right now, I have been using the long-form syntax to set a bit of a register, e.g.
etl::io_port_rw<uint32_t> ctrl;
ctrl = ctrl | 1;

[jwellbelove]

I am in the process of adding several operators.

|=
&=
^=
~

Also see this on Slack
IO port class change proposal

[jwellbelove]

Fixed 20.39.3