i2creg, onewirereg, spireg: augment Ref to include the pins

[maruel]

The goal is to be able to present the pin used by each I²C/1-wire/SPI port/bus without having to open the port/bus, as this is currently the case.

To achieve this, the corresponding Ref needs to be augmented with the corresponding pin name or reference (to be determined). This in itself isn't so bad and could be not considered a breaking change.

The breaking change is that this information needs to be passed to the Register() function, otherwise the register function would have to open the port/bus itself, which would slow down registration and would potentially cause unintended side effects. So if the Register() function needs to be changed, this is a breaking change.

Ref:

• https://periph.io/x/periph/conn/spi/spireg#Ref
• https://periph.io/x/periph/conn/i2c/i2creg#Ref
• https://periph.io/x/periph/conn/onewire/onewirereg#Ref

[maruel]

In the meantime this can be implemented without API breaking by adding a new function RegisterWithPins()

[maruel]

Ported to periph/conn#31.