i40e: use common failure flow

As mentioned by Joe Perches, we should be using
foo = alloc(...)
if (!foo)
	return -ENOMEM;

return 0;

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
CC: Joe Perches <joe@perches.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -101,10 +101,10 @@ int i40e_allocate_dma_mem_d(struct i40e_hw *hw, struct i40e_dma_mem *mem,
 	mem->size = ALIGN(size, alignment);
 	mem->va = dma_zalloc_coherent(&pf->pdev->dev, mem->size,
 				      &mem->pa, GFP_KERNEL);
-	if (mem->va)
-		return 0;
+	if (!mem->va)
+		return -ENOMEM;
 
-	return -ENOMEM;
+	return 0;
 }
 
 /**
@@ -136,10 +136,10 @@ int i40e_allocate_virt_mem_d(struct i40e_hw *hw, struct i40e_virt_mem *mem,
 	mem->size = size;
 	mem->va = kzalloc(size, GFP_KERNEL);
 
-	if (mem->va)
-		return 0;
+	if (!mem->va)
+		return -ENOMEM;
 
-	return -ENOMEM;
+	return 0;
 }
 
 /**