sparc64: fix initrd loading

sparc64: fix initrd loading

Initrd load address is too low, it conflicts with kernel load
address:
rom: requested regions overlap (rom phdr #0: /tmp/vmlinux-debian-6.0.4-sparc64. free=0x0000000000742519, addr=0x0000000000400000)
rom loading failed

Fix by making the initrd address variable, load initrd after kernel
image. Use 64 bit variables instead of longs or 32 bit types.

Tested-by: Artyom Tarasenko <atar4qemu@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>