Fix Incorrect Use of Interrupt Executor for Audio Callback

[Dicklessgreat]

In looper example, I found things are not set up correctly, although it works by some miracle.

Steps to fix

• Should unmask interrupt
• not SAI1, but DMA1_STR1(need to be investigated)?
• replace interface.start() with interface.setup_and_release()(to stop internal loop in Interface::start())