[bsp][wch]:adapt wch risc serial_v2

Author: CYFS3

bsp/wch/risc-v/Libraries/ch32_drivers/SConscript

@@ -10,7 +10,10 @@ if  GetDepend('SOC_RISCV_FAMILY_CH32'):
         src += ['drv_gpio.c']
 
     if GetDepend('BSP_USING_UART'):
-        src += ['drv_usart.c']
+        if GetDepend('RT_USING_SERIAL_V2'):
+            src += ['drv_usart_v2.c']
+        else:
+            src += ['drv_usart.c']
 
     if GetDepend('BSP_USING_ADC'):
         src += ['drv_adc.c']