Impl Peripheral for I2s trait

[bbutkovic]

This PR changes the I2s trait so that it is a superset of the Peripheral trait.

I recently got into a situation where I was trying to pass a PeripheralRef<'_, I2s> into I2sDriver::new_std_tx and found it problematic because the I2s trait does not necessarily guarantee it is a Peripheral, rather I2S0 and I2S1 structs implement Peripheral, making it hard to go about generic implementations.

This change will make it a little bit easier to work with the API when dealing with generics.

[ivmarkov]

This PR changes the I2s trait so that it is a superset of the Peripheral trait.

I recently got into a situation where I was trying to pass a PeripheralRef<'_, I2s> into I2sDriver::new_std_tx and found it problematic because the I2s trait does not necessarily guarantee it is a Peripheral, rather I2S0 and I2S1 structs implement Peripheral, making it hard to go about generic implementations.

This change will make it a little bit easier to work with the API when dealing with generics.

Why do you need to use PeripheralRef in your own code in the first place? The only reason why this type is public is so that it can be re-used in the esp-idf-svc crate. Yes, I know this is a bit of a code smell, but it is not supposed to be used by users directly.

So can you elaborate?

[bbutkovic]

The only reason why this type is public is so that it can be re-used in the esp-idf-svc crate.

It looks like I misunderstood the documentation then, my bad!

As I mentioned in #334, I'm working on a wrapper around the I2S driver and without the reconfiguration support I found it suitable to store a PeripheralRef in my struct and then use that later to create the I2s driver.

[ivmarkov]

@bbutkovic Were you able to NOT use PeripheralRef in your code? It should be well possible. I really don't think we can proclaim I2c as extending Peripheral. Does not feel right...