rename hello-debufs to id_jiff_foo_debufs

Rename hello-debufs to id_jiff_foo_debufs since it contains all three of
these components.  Synchronize code with id_debugfs.
id_jiff_foo_debufs: rm README, rm id-bad2.txt

Remove the out of data README.  Update the test script to also remove
the id-bad2.txt file.
add jiff_debugfs driver
id_jiff_foo_debugfs: ignore id-bad2.txt
fix jiff_debugfs name
add foo_debugfs driver
id_jiff_foo_debugfs: 4096 limit in test.sh

Fix the test script so it only transfers one page size.  This avoids the
transfer error message when it tries to transfer more than this amount.
add foo_debugfs to README
organize id_jiff_foo in to their own directory

Organize the id_jiff_foo drivers in to their own directory to make it
less cluttered.