xen: Switch to use kmemdup() helper

Use kmemdup() helper instead of open-coding to
simplify the code.
Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Chen Jiahao <chenjiahao16@huawei.com>
Link: https://lore.kernel.org/r/20230815092434.1206386-1-ruanjinjie@huawei.comSigned-off-by: Juergen Gross <jgross@suse.com>

drivers/xen/xen-acpi-processor.c

@@ -473,11 +473,8 @@ static int xen_upload_processor_pm_data(void)
 		if (!_pr)
 			continue;
 
-		if (!pr_backup) {
-			pr_backup = kzalloc(sizeof(struct acpi_processor), GFP_KERNEL);
-			if (pr_backup)
-				memcpy(pr_backup, _pr, sizeof(struct acpi_processor));
-		}
+		if (!pr_backup)
+			pr_backup = kmemdup(_pr, sizeof(*_pr), GFP_KERNEL);
 		(void)upload_pm_data(_pr);
 	}