[config] disable ui* directive in ASIC_MANUAL_INPUTS mode

[proppy]

When the mode is set to ASIC_MANUAL_INPUTS, it would be nice to disable the following directives automatically or to produce a meaningful error on load:

• uio_oe_pico
• ui_in
• uio_in

In particular setting uio_oe_pico to 0xff and any of the uio_in bits has the undesired effect of pulling all the uios up:

  uio0 IN 1
  uio1 IN 1
  uio2 IN 1
  uio3 IN 1
  uio4 IN 1
  uio5 IN 1
  uio6 IN 1
  uio7 IN 1