Bug 12283

Building a fitImage that include an initramfs force the kernel to depends on
rootfs.  This in turn cause rebuilding anything on any change.

For example, if the image is not included, building an out-of-tree kernel module
require pretty much just building the kernel + the module.  Yet, when you 
enable fitImage, building the same out-of-tree kernel module force re-building 
all the user space application as well.

Also, the image creation, fit or wic should not be kernel specific.  The code
found in kernel-fitimage.bbclass create an ITS file and then call uboot-mkimage.
There is nothing there that is kernel specific.

This code should be done within the image recipe, once the kernel uImage and the rootfs has been built, as is other image type.

Now I understand that if INITRAMFS_IMAGE_BUNDLE is set to 1 that the kernel need to be involved, but when INITRAMFS_IMAGE_BUNDLE is set to 0, there are no valid reason to have the kernel create the image itself instead of the image recipe creating the image and removing that kernel/rootfs dependency.