[yocto] initramfs support in Yocto

[Jeremy Puhlman]

> Can you be more specific about what you are looking for? When you build
> an image with the cpio.gz image type, you can boot that as an initramfs
> with the following kernel command line:
>
> initrd=core-image-minimal-fri2.cpio.gz root=/dev/ram0
>
> If you are looking for something beyond that, please elaborate.
>

When most people refer to initramfs support it is compiling a built
image in to the kernel binary(e.g.  CONFIG_INITRAMFS_SOURCE).
INITRAMFS_IMAGE
is part of the kernel class that should enable that in the build.