Fix esp-idf build: add esp_timer.h, correct uart_get_buffered_data_len usage

src/main.c

@@ -3,6 +3,7 @@
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
 #include "esp_log.h"
+#include "esp_timer.h"
 #include "driver/uart.h"
 #include "driver/rmt_tx.h"
 #include "led_strip_encoder.h"
@@ -145,8 +146,9 @@ void app_main(void){
     int line_pos=0;
 
     while(1){
-        int ch;
-        while(uart_get_buffered_data_len(UART_NUM_0) > 0){
+        size_t buffered = 0;
+        uart_get_buffered_data_len(UART_NUM_0, &buffered);
+        while(buffered > 0){
             uint8_t c;
             int len = uart_read_bytes(UART_NUM_0,&c,1,0);
             if(len>0){