arm/xen: Delete an error message for a failed memory allocation in __set_phys_to_machine_multi()

Omit an extra message for a memory allocation failure in this function.

This issue was detected by using the Coccinelle software.

Link: http://events.linuxfoundation.org/sites/events/files/slides/LCJ16-Refactor_Strings-WSang_0.pdf


Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>