kernel-fitimage.bbclass: Fix the dependency issue while generating fitimage_initramfs
When building fitimage_initramfs, the correct depedency is to build
after do_bundle_initramfs. We can run into the following dependency
issue
DEBUG: Python function extend_recipe_sysroot finished
DEBUG: Executing shell function do_assemble_fitimage_initramfs
aarch64-xilinx-linux-objcopy: 'vmlinux': No such file
This happens because initramfs renames vmlinux to vmlinux.bak while
generating vmlinux.initramfs, there is a chance that fitimage_initramfs
can also start during this process and create the above issue.
This patch resolve the dependency issue by running fitimage_initramfs
task after do_bundle_initramfs
