net: lib: lwm2m: Use defines for update state and result pathstrs
net: lib: lwm2m: Use defines for update state and result pathstrs

Use defines instead of hardcoded strings to avoid future errors if the
values would change.

Signed-off-by: Andreas Pettersson <ca9ce63712ec3fe3a5fc6a646ce06dd513e8b23b@gmail.com>

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