dm writecache: remove disabled code in memory_entry()

This dead branch was missed during review.  It only makes memory_entry()
more inefficient due to needless call to is_power_of_2(), etc.
Reported-by: shenghui <shhuiw@foxmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-writecache.c

@@ -350,10 +350,7 @@ static struct wc_memory_superblock *sb(struct dm_writecache *wc)
 
 static struct wc_memory_entry *memory_entry(struct dm_writecache *wc, struct wc_entry *e)
 {
-	if (is_power_of_2(sizeof(struct wc_entry)) && 0)
-		return &sb(wc)->entries[e - wc->entries];
-	else
-		return &sb(wc)->entries[e->index];
+	return &sb(wc)->entries[e->index];
 }
 
 static void *memory_data(struct dm_writecache *wc, struct wc_entry *e)