Esp32 i2s jitter (#754)

* ESP32 I2s clock divider calculations improved
* ESP32 I2s DMA silence block data improved

extras/debug/esp32/I2sDump/I2sDump.ino

@@ -0,0 +1,26 @@
+#include <NeoPixelBus.h>
+
+#if !defined(ARDUINO_ARCH_ESP32)
+@error ESP32 Supported Only
+#endif
+
+void setup()
+{
+    Serial.begin(115200);
+    while (!Serial); // wait for serial attach
+}
+
+void loop()
+{
+    Serial.println();
+    Serial.println();
+    Serial.println("I2S0: ");
+    i2sDump(0);
+
+    Serial.println();
+    Serial.println();
+    Serial.println("I2S1: ");
+    i2sDump(1);
+
+    delay(10000);
+}