After we bumped u-boot to version v2022.10, a couple of boards
stopped booting because the CONFIG_SPL_STACK value used in our
u-boot config was too low for that SOC. This change drops explicit
CONFIG_SPL_STACK defination from the affected boards.
The boards confirmed to have the issues were Orange Pi 3 LTS and
NanoPi Neo Black2 but I suspect that NanoPi K1 plus is also affected
hence similar change is done for that as well
71295431b8