Fix uart tx function block issue

To enable tx empty interrupt each time the tx ringbuffer get filled, so that tx function will not block if tx data length is larger than tx ringbuffer size.
Reported from customer of Audio team.

components/driver/uart.c

@@ -806,9 +806,9 @@ static int uart_tx_all(uart_port_t uart_num, const char* src, size_t size, bool
             xRingbufferSend(p_uart_obj[uart_num]->tx_ring_buf, (void*) (src + offset), send_size, portMAX_DELAY);
             size -= send_size;
             offset += send_size;
+            uart_enable_tx_intr(uart_num, 1, UART_EMPTY_THRESH_DEFAULT);
         }
         xSemaphoreGive(p_uart_obj[uart_num]->tx_mux);
-        uart_enable_tx_intr(uart_num, 1, UART_EMPTY_THRESH_DEFAULT);
     } else {
         while(size) {
             //semaphore for tx_fifo available