staging: android: ion: Use ERR_CAST instead of ERR_PTR

Fix the following coccinelle warnings in ion.c:
drivers/staging/android/ion/ion.c:511:9-16: WARNING: ERR_CAST can be used with buffer
drivers/staging/android/ion/ion.c:218:9-16: WARNING: ERR_CAST can be used with table
drivers/staging/android/ion/ion.c:1150:9-16: WARNING: ERR_CAST can be used with dmabuf

Signed-off-by: Iulia Manda <[e-mail]>
Acked-by: Paul E. McKenney <[e-mail]>
Signed-off-by: Peter P Waskiewicz Jr <[e-mail]>

drivers/staging/android/ion/ion.c

···
 	if (IS_ERR(table)) {
 		heap->ops->free(buffer);
 		kfree(buffer);
-		return ERR_PTR(PTR_ERR(table));
+		return ERR_CAST(table);
 	}
 	buffer->sg_table = table;
 	if (ion_buffer_fault_user_mappings(buffer)) {
···
 		return ERR_PTR(-ENODEV);
 
 	if (IS_ERR(buffer))
-		return ERR_PTR(PTR_ERR(buffer));
+		return ERR_CAST(buffer);
 
 	handle = ion_handle_create(client, buffer);
 
···
 
 	dmabuf = dma_buf_get(fd);
 	if (IS_ERR(dmabuf))
-		return ERR_PTR(PTR_ERR(dmabuf));
+		return ERR_CAST(dmabuf);
 	/* if this memory came from ion */
 
 	if (dmabuf->ops != &dma_buf_ops) {