Fix loading of unstripped ELF PROM image

#define KERNEL_LOAD_ADDR     0x00004000

#define CMDLINE_ADDR         0x007ff000

#define INITRD_LOAD_ADDR     0x00800000

#define PROM_SIZE_MAX        (512 * 1024)

#define PROM_SIZE_MAX        (1024 * 1024)

#define PROM_VADDR           0xffd00000

#define PROM_FILENAME        "openbios-sparc32"

#define CFG_ADDR             0xd00000510ULL