1. modify at32_msp default configuration 2. add hwtimer driver and fix up some driver errors 3. update related files

Author: sheltonyu

bsp/at32/Libraries/rt_drivers/SConscript

@@ -21,6 +21,9 @@ if GetDepend(['BSP_USING_SERIAL']):
 if GetDepend(['BSP_USING_PWM']):
     src += ['drv_pwm.c']
 
+if GetDepend(['BSP_USING_HWTIMER']):
+    src += ['drv_hwtimer.c']
+
 if GetDepend(['BSP_USING_SPI']):
     src += ['drv_spi.c']