The loopback on the unused gpio inputs consumes routing resources
while does not gives any value for the software.
Connect these lines to zero instead.
Some projects use the ad_iobuf on IOs that are not bidirectional
producing synthesis warnings.
The change fixes warnings like:
[Synth 8-6104] Input port 'gpio_bd_i' has an internal driver
[Synth 8-6104] Input port 'gpio_status' has an internal driver
- remove interrupts from system_top
- for all suported carriers:
- remove all interrupt bd pins
- connect to GND all initial unconnected interrupt pins
- update ad_cpu_interrupt procedure to disconnect a interrupt from GND
before connectiong it to another pin.