staging: ion: Remove explicit NULL comparison

Rewrite explicit NULL comparison in its simpler form.
<smpl>
@NULL_REPLACE@
expression e;
@@

-e == NULL
+ !e

Signed-off-by: Muhammad Falak R Wani <falakreyaz@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion_heap.c

@@ -56,7 +56,7 @@ void *ion_heap_map_kernel(struct ion_heap *heap,
 	vaddr = vmap(pages, npages, VM_MAP, pgprot);
 	vfree(pages);
 
-	if (vaddr == NULL)
+	if (!vaddr)
 		return ERR_PTR(-ENOMEM);
 
 	return vaddr;