tlsr82/serial: clear uart tx index when uart_reset called.

Otherwise, after the rx error occur, the tx output will be
out of sequence, for example:
normal log:
[   30.163000] 12345678abcdefgh
[   30.666000] 12345678abcdefgh
[   31.169000] 12345678abcdefgh
[   31.672000] 12345678abcdefgh
[   32.175000] 12345678abcdefgh
[   32.678000] 12345678abcdefgh
[   33.181000] 12345678abcdefgh

error log:
he 7 .20]0003 127456c8abgdefch
gde [6.707002] 16345b78afcde
fcde
fghe10010] 5234a678ebcd
 77 713 00]41238567dabchefgd
che 7 .21]0003 127456c8abgdefch
gde [8.709002] 16345b78afcde
fcde

Signed-off-by: wangbowen6 <wangbowen6@xiaomi.com>

arch/arm/src/tlsr82/tlsr82_serial.c

@@ -331,32 +331,51 @@ static uart_dev_t g_uart0_dev =
  ****************************************************************************/
 
 /****************************************************************************
- * Name: uart_reset
+ * Name: uart_clr_rx_index
  *
  * Description:
- *   Reset the uart hardware, the software pointer must be set to zero
- *   (function uart_clr_rx_index() must be called).
+ *   Clear the uart receive software pointer, this function must be called
+ *   after wakeup from power-saving mode or reset uart.
  *
  * Parameters:
+ *   uart_num  - the uart hardware index
+ *
+ * Returned Values:
  *   void
  *
+ ****************************************************************************/
+
+static inline void uart_clr_rx_index(int uart_num)
+{
+  uart_rxindex = 0;
+}
+
+/****************************************************************************
+ * Name: uart_clr_tx_index
+ *
+ * Description:
+ *   Clear the uart transimit software pointer, this function must be called
+ *   after wakeup from power-saving mode or reset uart.
+ *
+ * Parameters:
+ *   uart_num  - the uart hardware index
+ *
  * Returned Values:
  *   void
  *
  ****************************************************************************/
 
-static inline void uart_reset(void)
+static inline void uart_clr_tx_index(int uart_num)
 {
-  RESET_RST0_REG |= RESET_RST0_UART;
-  RESET_RST0_REG &= ~RESET_RST0_UART;
+  uart_txindex = 0;
 }
 
 /****************************************************************************
  * Name: uart_reset
  *
  * Description:
- *   Clear the uart receive software pointer, this function must be called
- *   after wakeup from power-saving mode or reset uart.
+ *   Reset the uart hardware, the software pointer must be set to zero
+ *   (function uart_clr_rx_index() must be called).
  *
  * Parameters:
  *   uart_num  - the uart hardware index
@@ -366,9 +385,12 @@ static inline void uart_reset(void)
  *
  ****************************************************************************/
 
-static inline void uart_clr_rx_index(int uart_num)
+static inline void uart_reset(int uart_num)
 {
-  uart_rxindex = 0;
+  RESET_RST0_REG |= RESET_RST0_UART;
+  RESET_RST0_REG &= ~RESET_RST0_UART;
+  uart_clr_rx_index(uart_num);
+  uart_clr_tx_index(uart_num);
 }
 
 /****************************************************************************
@@ -999,7 +1021,7 @@ static int tlsr82_uart_setup(struct uart_dev_s *dev)
 
   /* Reset the uart */
 
-  uart_reset();
+  uart_reset(priv->port);
 
   /* Uart communication parameters config
    * TODO: unity below functions to uart_format_config()
@@ -1071,10 +1093,9 @@ static int UART_RAMCODE tlsr82_interrupt(int irq, void *context, void *arg)
 
       uart_irq_clr(priv->port, UART_IRQ_CLR_RX);
 
-      /* uart_reset() clear hardware pointer, and clear software pointer */
+      /* uart_reset() clear hardware and software fifo index */
 
-      uart_reset();
-      uart_clr_rx_index(priv->port);
+      uart_reset(priv->port);
     }
 
 #ifdef CONFIG_SERIAL_TXDMA