net: ethernet: ibm: ehea: ehea_qmr.c: Fix for possible null pointer dereference

There is otherwise a risk of a possible null pointer dereference.

Was largely found by using a static code analysis program called cppcheck.
Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/ehea/ehea_qmr.c

@@ -103,12 +103,14 @@ static int hw_queue_ctor(struct hw_queue *queue, const u32 nr_of_pages,
 
 static void hw_queue_dtor(struct hw_queue *queue)
 {
-	int pages_per_kpage = PAGE_SIZE / queue->pagesize;
+	int pages_per_kpage;
 	int i, nr_pages;
 
 	if (!queue || !queue->queue_pages)
 		return;
 
+	pages_per_kpage = PAGE_SIZE / queue->pagesize;
+
 	nr_pages = queue->queue_length / queue->pagesize;
 
 	for (i = 0; i < nr_pages; i += pages_per_kpage)