schematic: clarify rotary encoder module

[grahamwhaley]

The rotary encoder I used was a module, that includes some pullups. Clarify the schematic around that area to make it clearer:

• how to wire up the module if you are using one
• what the module provides, and thus help define how to wire up a 'naked' module

Signed-off-by: Graham Whaley graham.whaley@gmail.com