MAINTAINERS: add @jciupis to IEEE 802.15.4 drivers collaborators
MAINTAINERS: add @jciupis to IEEE 802.15.4 drivers collaborators

Adds @jciupis as collaborator of IEEE 802.15.4 drivers.

Signed-off-by: Jedrzej Ciupis <6236c7d07f3a915f3607d3bfbdd3ebf209c7426c@nordicsemi.no>

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