x300: Cleaned up DAC ctrl and clock init logic

- DAC: Squashed configuration into 2 main operations: reset and reset_and_resync
- DAC: Put in sleep mode during configuration
- DAC: Synchronize only if streaming to more than one DAC
- DAC: Use falling edge sync mode
- DAC: Fixed power up/down settings
- DAC: Frontend sync failure is fatal
- Clocks: Refactored clock source change logic
- Clocks: Cleaned up init and lock-check sequence