[bsp/n32g452xx] In drv_pwm.c, variable meaning is different with RT-Thread interface definition. Fixed and tested. [bsp/n32g452xx] Add support for UART4/UART5. [bsp/n32g452xx] In drv_gpio.c Modify "N32F10X_PIN_NUMBERS" to "N32G45X_PIN_NUMBERS".
1. remove gpio&uart INIT_BOARD_EXPORT 2. init gpio&uart in rt_hw_board_init 3. add clock driver
[AT32] 完善ADC驱动
[add] N32G452 BSP