i2c comment for SPDIF

esp-idf i2c.c *must* be patched at 2 different places for SPDIF to work

components/squeezelite/output_i2s.c

@@ -234,6 +234,11 @@ void output_init_i2s(log_level level, char *device, unsigned output_buf_size, ch
 	set_i2s_pin(spdif_config, &i2s_spdif_pin);										
 	set_i2s_pin(dac_config, &i2s_dac_pin);										
 
+	/* BEWARE: i2s. must be patched to set tx_msb_right/rx_msb_right to 1
+	 * or SPDIF will not work. These settings are not accessible from
+	 * userland and I don't know why
+	 */
+
 	// common I2S initialization
 	i2s_config.mode = I2S_MODE_MASTER | I2S_MODE_TX;
 	i2s_config.channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT;