arm/xen: Improve a size determination in __set_phys_to_machine_multi()

Replace the specification of a data structure by a pointer dereference
as the parameter for the operator "sizeof" to make the corresponding size
determination a bit safer according to the Linux coding style convention.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c
index 0ed01f2..11e7843 100644
--- a/arch/arm/xen/p2m.c
+++ b/arch/arm/xen/p2m.c
@@ -144,7 +144,7 @@
 		return true;
 	}
 
-	p2m_entry = kzalloc(sizeof(struct xen_p2m_entry), GFP_NOWAIT);
+	p2m_entry = kzalloc(sizeof(*p2m_entry), GFP_NOWAIT);
 	if (!p2m_entry) {
 		pr_warn("cannot allocate xen_p2m_entry\n");
 		return false;