xen/unpopulated-alloc: Drop check for virt_addr_valid() in fill_list()

If memremap_pages() succeeds the range is guaranteed to have proper page
table, there is no need for an additional virt_addr_valid() check.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/1639080336-26573-2-git-send-email-olekstysh@gmail.com


Signed-off-by: Juergen Gross <jgross@suse.com>