Fix data abort caused by mis-aligning FIT data

Attempting to place device tree immediately after an image in memory can lead
to mis-aligned data accesses if that image size is not divisible by the
alignment requirements of the architecture.

Data aborts caused by this were observed on a custom Marvel A388 based system,
where the image was a uboot FIT file. The total size varies depending on the
uboot device tree size, which does not always lead to correct alignment.

The minimum alignment specified for ARM [1] and ARM64 [2] linux booting has been
used

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/booting.rst#n126
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm64/booting.rst#n45



Signed-off-by: Reuben Dowle <reuben.dowle@4rf.com>