MAINTAINERS: Add SeppoTakalo as a collaborator for LwM2M
MAINTAINERS: Add SeppoTakalo as a collaborator for LwM2M

Add SeppoTakalo as a collaborator for LwM2M subsystem and
the client sample.

Signed-off-by: Seppo Takalo <a79cb1c919d7203cb1925e0654c27476c1374442@nordicsemi.no>

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