Add COPI/CIPO legend to schematics

[esden]

It is not always clear for everyone what COPI/CIPO stands for.

• COPI: Controller Out Peripheral In (used to be MOSI)
• CIPO: Controller In Peripheral Out (used to be MISO)

This should be added to the schematics to avoid ambiguity.

For additional information refer to the OSHWA resolution.

[esden]

It was brought to our attention that there is a new resolution.

So in the process of documenting the change in the schematics it would probably be a good idea to switch to the new order:

• PICO: Peripheral In Controller Out
• POCI: Peripheral Out Controller In