removing fdt_high from default set of variables for, dragonboard410c config

removing fdt_high from default set of variables for, dragonboard410c config

When using fitImage in AARCH64, the fdt is only 4 byte aligned.
According to linux kernel -> Documentation/arm64/booting.txt, the
fdt *must* be 8 byte aligned. Therefore, it is somewhat random,
if you build a kernel that the fdt is 4 or 8 byte aligned.
Removing fdt_high (or changing it to a valid 8 byte aligned
address) solves this issue.

Signed-off-by: Matthias Schoepfer <matthias.schoepfer@ithinx.io>
CC: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>