esp32/machine_uart: Remove UART event queue object.

This event queue has UART events posted to it and they need to be drained
for it to operate without error.  The queue is not used by the uPy UART
class so it should be removed to prevent the IDF emitting errors.

Fixes #3704.

ports/esp32/machine_uart.c

@@ -52,8 +52,6 @@ typedef struct _machine_uart_obj_t {
 
 STATIC const char *_parity_name[] = {"None", "1", "0"};
 
-QueueHandle_t UART_QUEUE[UART_NUM_MAX] = {};
-
 /******************************************************************************/
 // MicroPython bindings for UART
 
@@ -242,7 +240,7 @@ STATIC mp_obj_t machine_uart_make_new(const mp_obj_type_t *type, size_t n_args,
     uart_param_config(self->uart_num, &uartcfg);
 
     // RX and TX buffers are currently hardcoded at 256 bytes each (IDF minimum).
-    uart_driver_install(uart_num, 256, 256, 10, &UART_QUEUE[self->uart_num], 0);
+    uart_driver_install(uart_num, 256, 256, 0, NULL, 0);
 
     mp_map_t kw_args;
     mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);