drivers: i2c: improve gd32 i2c driver stability
drivers: i2c: improve gd32 i2c driver stability

This split the repeated START condition to STOP + START conditions.

The old implement may cause undefined behavior for gd32 i2c, like
enter STOP condition accidentally.

Signed-off-by: HaiLong Yang <c5b53c3148d79a31d58d6febcc7e03b084440d0f@brainco.cn>

zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr