xen: Replace lkml.org links with lore

As started by commit 05a5f51ca566 ("Documentation: Replace lkml.org
links with lore"), replace lkml.org links with lore to better use a
single source that's more likely to stay available long-term.

Signed-off-by: Kees Cook <[e-mail]>
Reviewed-by: Boris Ostrovsky <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Boris Ostrovsky <[e-mail]>

drivers/xen/xen-acpi-processor.c

···
  * Copyright 2012 by Oracle Inc
  * Author: Konrad Rzeszutek Wilk <[e-mail]>
  *
- * This code borrows ideas from https://lkml.org/lkml/2011/11/30/249
+ * This code borrows ideas from
+ * https://lore.kernel.org/lkml/[e-mail]
  * so many thanks go to Kevin Tian <[e-mail]>
  * and Yu Ke <[e-mail]>.
  */