Remove the acpi loading function from elf_loader, rawimage_loaer and
bzimage_loader, and call it together in vm_sw_loader.
Now the vm_sw_loader's job is not just loading sw, so we rename it to
prepare_os_image.
Tracked-On: #6323
Signed-off-by: Zhou, Wu <wu.zhou@intel.com>
Reviewed-by: Victor Sun <victor.sun@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>