Merge patch series "mkimage: fit: various fixes in fit_{import,extract}_data"

Quentin Schulz <foss+uboot@0leil.net> says:

I had to hunt down a difference between the FIT after running mkimage
once and after running it twice. The use-case is typically U-Boot
generating an unsigned FIT and then calling mkimage manually to sign it
outside any build system.

The issue can be reproduced with the following

make CROSS_COMPILE=aarch64-linux-gnu- BUILD_TAG= SOURCE_DATE_EPOCH=0 O=build/ringneck ringneck-px30_defconfig
make CROSS_COMPILE=aarch64-linux-gnu- BUILD_TAG= SOURCE_DATE_EPOCH=0 O=build/ringneck -j`nproc`
cd build/ringneck
cp ./simple-bin.fit.itb ./simple-bin.foo.fit
cp ./simple-bin.fit.itb ./simple-bin.foo2.fit
BUILD_TAG= SOURCE_DATE_EPOCH=0 ./tools/mkimage -E -t -B 200 -F ./simple-bin.foo.fit
BUILD_TAG= SOURCE_DATE_EPOCH=0 ./tools/mkimage -E -t -B 200 -F ./simple-bin.foo2.fit
BUILD_TAG= SOURCE_DATE_EPOCH=0 ./tools/mkimage -E -t -B 200 -F ./simple-bin.foo2.fit

then compare the output of

dtc -I dtb -O dts simple-bin.foo.fit
dtc -I dtb -O dts simple-bin.foo2.fit

data-size and data-offset properties are swapped.

While going through the code, I identified a few theoretical issues
possibly triggered by not checking the return code of fdt_setprop so
those are added. Not tested outside of building.

Link: https://lore.kernel.org/r/20250923-mkimage-2-runs-data-size-v1-0-ef3fa57e9645@cherry.de