staging: olpc_dcon: provide detailed FB_OLPC_DCON help section

The FB_OLPC_DCON help section is to short according to checkpatch.pl.
We want more information about the controller type, its task, its video
pipeline position and so on.

There are no style issues, remove checkpatch.pl TODO entry.

Signed-off-by: Jens Frederich <jfrederich@gmail.com>