bsp: cvitek: fix cvitek uart driver can not repeat configure

After first called from uart open, the dw8250_uart_configure
API cannot be called again. Otherwise, this will mess up the
device, and uart will not act properly to interrupt again.

Analysis: Configure uart device will close recive interrupte,
causing uart device to malfunction.

Solution: After configure uart device, enable the device's
recive interrupte.

Signed-off-by: Shicheng Chu <1468559561@qq.com>
Reviewed-by: Chen Wang <unicorn_wang@outlook.com>

bsp/cvitek/drivers/drv_uart.c

@@ -115,6 +115,7 @@ static rt_err_t dw8250_uart_configure(struct rt_serial_device *serial, struct se
     rt_base_t base;
     struct hw_uart_device *uart;
     int clock_divisor;
+    int last_ier_state;
 
     RT_ASSERT(serial != RT_NULL);
     uart = (struct hw_uart_device *)serial->parent.user_data;
@@ -122,6 +123,7 @@ static rt_err_t dw8250_uart_configure(struct rt_serial_device *serial, struct se
 
     while (!(dw8250_read32(base, UART_LSR) & UART_LSR_TEMT));
 
+    last_ier_state = dw8250_read32(base, UART_IER);
     dw8250_write32(base, UART_IER, 0);
     dw8250_write32(base, UART_MCR, UART_MCRVAL);
     dw8250_write32(base, UART_FCR, UART_FCR_DEFVAL);
@@ -132,6 +134,8 @@ static rt_err_t dw8250_uart_configure(struct rt_serial_device *serial, struct se
     clock_divisor = DIV_ROUND_CLOSEST(UART_INPUT_CLK, 16 * serial->config.baud_rate);
     dw8250_uart_setbrg(base, clock_divisor);
 
+    dw8250_write32(base, UART_IER, last_ier_state);
+
     return RT_EOK;
 }