After rework of the file system API, the size of ext4
write was missed. This causes printing unreliable write
size at the end of the file system write operation.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Tested-by: Stephen Warren <swarren@nvidia.com>