[GD32] fix bug on spi driver (#6636)
[GD32] fix bug on spi driver (#6636)

* fix bug on spi driver

* [gd32] fix bugs on spi driver
RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread