The nRF52833 has only 512 kB of flash. The .dts file was incorrect, as a
product of having it forked from the nRF52840 .dts files, which has 1 MB
of flash.
The new, correct partitions are closely related to the
[nrf52833dk](ec52722861/boards/arm/nrf52833dk_nrf52833/nrf52833dk_nrf52833.dts (L215)).
The new SDK requires 802.15.4 to be enabled in the board DTS file.
Also disable IPv6 explicitly to avoid compile errors related to its
network stack, since it is not used currently.
Closes#94