Valgrind reports that when loading a non-ELF kernel, kernel_top may be used
uninitialised when checking for an initrd.
Since there are no known non-ELF kernels for SPARC64 then we can simply
initialise kernel_top to 0 and then skip the initrd load process if it hasn't
been set by load_elf().
Reported-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>