dma_buf: no need to bother with file_inode()->i_mapping

->f_mapping will do just fine
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/dma-buf/udmabuf.c

@@ -210,7 +210,7 @@ static long udmabuf_create(struct miscdevice *device,
 		memfd = fget(list[i].memfd);
 		if (!memfd)
 			goto err;
-		mapping = file_inode(memfd)->i_mapping;
+		mapping = memfd->f_mapping;
 		if (!shmem_mapping(mapping) && !is_file_hugepages(memfd))
 			goto err;
 		seals = memfd_fcntl(memfd, F_GET_SEALS, 0);