add option to change the ADC NQZ

[meeg]

The RF-ADC has a Nyquist zone setting, similar to the RF-DAC. It's not clear what this setting does (something related to the automatic RF-ADC calibration?), and in past testing we've never seen an effect from changing this setting. Still, it seems reasonable to make it accessible. This won't impact any existing code.

• https://docs.xilinx.com/r/en-US/pg269-rf-data-converter/RF-ADC-Nyquist-Zone-Operation
• https://support.xilinx.com/s/question/0D52E00006hpjaYSAQ/nyquist-zones-in-rf-soc-adc
• https://support.xilinx.com/s/question/0D52E00006yodA6SAI/what-is-effect-of-adc-nyquist-zone-settings-what-should-i-expectwhat-is-effect-of-calibration-mode-settings-what-should-i-expect