qcacmn: Add NULL check while iterating sgl entries

__qdf_dma_get_sgtable_dma_addr() iterates through sgl entries
without appropriately checking for NULL pointers before attempting
to access them.

Fix the above-mentioned issue by adding a NULL check before access.

Change-Id: I7456db834f71b9b5cf3cb254526177b9fdcee664
CRs-Fixed: 2448239

qdf/linux/src/i_qdf_mem.h

@@ -288,8 +288,12 @@ __qdf_dma_get_sgtable_dma_addr(struct sg_table *sgt)
 	struct scatterlist *sg;
 	int i;
 
-	for_each_sg(sgt->sgl, sg, sgt->nents, i)
+	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
+		if (!sg)
+			break;
+
 		sg->dma_address = sg_phys(sg);
+	}
 }
 
 /**