The default loadaddr has changed from kernel 4.1 (fsimx6-V3.1) to 4.9 (fsimx6-B2020.04). Now it is 11000000 (previously 10800000) and the device tree is loaded to 12000000 (previously 11000000). When you still have the old settings, you most probably did not erase the U-Boot environment when upgrading U-Boot. Issue the following commands in U-Boot
nand erase.part UBootEnv
Now you should have the correct default settings and the kernel will boot. Of course if you had set some own variables, you have to do this again now.
The reason for this change is that the new kernel image uses more space when unzipped. With the old settings, it will overwrite the device tree that is stored behind it, which causes the kernel to fail. This is why it still works with your kernel that is slightly smaller.
Thanks for pointing out the problem with the clock settings. This is in fact a bad setting in the armstonea9qdl.dtsi device tree. I have attached a small patch that will fix this. Apply to the source code with the following command
Please note the less-than character for input redirection.
Your F&S Support Team