Add I2S support

This adds I2S support from Genuine MicroPython by Mike Teachman.
Thanks, @miketeachman!

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 \

esp32/hal/esp32_mphal.h

@@ -30,4 +30,7 @@ void mp_hal_set_interrupt_char(int c);
 void mp_hal_set_reset_char(int c);
 void mp_hal_reset_safe_and_boot(bool reset);
 
+// I2S driver
+#define machine_pin_get_id(pin) pin_find(pin)->pin_number
+
 #endif // _INCLUDED_MPHAL_H_