4MSPS script with FIR filters

- Add FIR filter search path in /usr/lib/ad9361/filter
- Add previous wimax filter tested with legacy driver
- Revise 4MSPS T2R2 script for new commands and IIO driver
- Add set_filter_fir_config command to ad9361
- Quash some debug and warning messages
- Set aux DAC for XO tuning