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>

drivers/macintosh/rack-meter.c

@@ -397,7 +397,7 @@ static int rackmeter_probe(struct macio_dev* mdev,
 	}
 
 	/* Create and initialize our instance data */
-	rm = kzalloc(sizeof(struct rackmeter), GFP_KERNEL);
+	rm = kzalloc(sizeof(*rm), GFP_KERNEL);
 	if (rm == NULL) {
 		printk(KERN_ERR "rackmeter: failed to allocate memory !\n");
 		rc = -ENOMEM;