How to build u-boot boot form qspi flash?
How to build should be described in the documentation(README). The used defconfig might not be that obvious.
export CROSS_COMPILE=<Vitis or SDK instalation dir(+version)>/gnu/aarch32/lin/gcc-arm-linux-gnueabi/bin/arm-linux-gnueabihf-
You need more than u-boot. u-boot is the second stage bootloader.
I'm not sure if you need some special settings for u-boot to boot from qspi. I'm guessing not.
I do not have much experience on booting from qspi. I've played with loading a hello world(and other baremetal projects) as packed in a boot.bin on the qspi via Vitis or SDK.
To boot a linux you need the dtb and kernel image, BOOT.BIN is not enough.
We have some example regarding this on pluto and m2k. Where the above and more are packed in a .frm