MAINTAINERS: update gd32 maintainers
MAINTAINERS: update gd32 maintainers

Promote HaiLong Yang @cameled as gd32 maintainer.

Signed-off-by: Gerson Fernando Budke <0ad1c92223f8f375c46e39c6141096f3d30896b4@gmail.com>

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