powerpc: Use sizeof(*foo) rather than sizeof(struct foo)

It's slightly less error prone to use sizeof(*foo) rather than
specifying the type.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
[mpe: Consolidate into one patch, rewrite change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/opal-hmi.c

@@ -314,7 +314,7 @@ static int opal_handle_hmi_event(struct notifier_block *nb,
 		pr_err("HMI: out of memory, Opal message event not handled\n");
 		return -ENOMEM;
 	}
-	memcpy(&msg_node->hmi_evt, hmi_evt, sizeof(struct OpalHMIEvent));
+	memcpy(&msg_node->hmi_evt, hmi_evt, sizeof(*hmi_evt));
 
 	spin_lock_irqsave(&opal_hmi_evt_lock, flags);
 	list_add(&msg_node->list, &opal_hmi_evt_list);