Add I2S support

This commit adds I2S support from Genuine MicroPython by Mike Teachman.

See also micropython/micropython#4471

Author: amotl

esp32/application.mk

@@ -133,6 +133,7 @@ APP_MODS_SRC_C = $(addprefix mods/,\
 	pybflash.c \
 	machspi.c \
 	machine_i2c.c \
+	machine_i2s.c \
 	machpwm.c \
 	machcan.c \
 	modmachine.c \