HV: Add elf loader sketch

This patch adds a function elf_loader() to load elf image.
It checks the elf header, get its 32/64 bit type, then calls
the corresponding loading routines, which are empty, and
will be realized later.

Tracked-On: #6323

Signed-off-by: Zhou, Wu <wu.zhou@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/common/vm_load.c

@@ -39,6 +39,11 @@ int32_t prepare_os_image(struct acrn_vm *vm)
 	case KERNEL_RAWIMAGE:
 		ret = rawimage_loader(vm);
 		break;
+#endif
+#ifdef CONFIG_GUEST_KERNEL_ELF
+	case KERNEL_ELF:
+		ret = elf_loader(vm);
+		break;
 #endif
 	default:
 		ret = -EINVAL;