Add I2S Slave Support For Teensy 4.0

[bthayer3]

Looks like the AudioInputI2Sslave_F32 is targeting an older teensy 3 board. Add a new logic section to support Teensy 4.0 board. I compared the logic used in the PJRC audio library and added this logic more so as an educated guess. It my testing it does work with some glitches though, I am probably testing this all wrong though as I don't have an oscilloscope.

Probably would also need the design tool with this i2sslaveinput drag and drop element. Didn't add that code yet as I think this slave code needs more work.

For reference: this is the code I was using in the Arduino sketch when I tested this. I was sending over 16 bit at 48 khz:

#include "OpenAudio_ArduinoLibrary.h"
#include "AudioStream_F32.h"
#include "USB_Audio_F32.h"
#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>

AudioInputI2Sslave_F32       audioInI2S1;
AudioOutputUSB_F32           audioOutUSB1;
AudioConnection_F32          patchCord1(audioInI2S1, 0, audioOutUSB1, 0);
AudioConnection_F32          patchCord2(audioInI2S1, 1, audioOutUSB1, 1);

void setup() {
  AudioMemory(30);  
  AudioMemory_F32(30);
}

void loop() {
}