Since https://github.com/ARM-software/arm-trusted-firmware/commit/94b2f94bd63258c300b53ad421488c3c4455712b, the FDT address needs to be 8-byte aligned. The FDT address as passed by U-Boot is correctly aligned when passed to TF-A. However, Rockchip's params_setup gives an unaligned buffer to fdt_open_into function which therefore fails the opening of the FDT in TF-A.
This only applies to master branch (post-v2.7.0).