[adc_ctrl] Fix adc interrupt synchronization
[adc_ctrl] Fix adc interrupt synchronization

- fixes #11759
- switch to prim_reqack instead of prim_pulse_sync
- since many events can occur during low power, split
  the sync source into staging and request.

Signed-off-by: Timothy Chen <d7b2ae30d8c0f215facd721941273067fd1d14a2@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan