Merge branch 'bugfix/openthread-uart-error' into 'master'

openthread: fix wrong OpenThread uart read return value handling

See merge request espressif/esp-idf!13909

components/openthread/port/esp_openthread_uart.c

@@ -119,7 +119,7 @@ esp_err_t esp_openthread_uart_process()
 
     if (rval > 0) {
         otPlatUartReceived(s_uart_buffer, (uint16_t)rval);
-    } else if (rval > 0) {
+    } else if (rval < 0) {
         if (errno != EAGAIN) {
             otLogWarnPlat("read uart failed: %d", errno);
             return ESP_FAIL;