uboot-imx

test/py: test_fs: add docstring comments to helper functions

After Siomon's comment, add a descriptive comment (docstring) to each of
helper functions in conftest.py. No functionality changed.

Signed-off-by: Akashi Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>