Allow the boot wrapper to obtain the vmlinux elf from an external
platform supplied location instead of embedding it at link time.
When used with the cpio library, the kernel can be stored as a file
an file in the initramfs, allowing the same (compressed) copy of
the vmlinux elf to be used for both the kernel to execute and any
user space tools such as kexec (for reboot), crash dump, or oprofile.