staging: olpc_dcon: Remove TODO item

All uses of old GPIO API have been converted to new API.
This item can be removed from TODO file.

Signed-off-by: Jerry Lin <wahahab11@gmail.com>
Link: https://lore.kernel.org/r/20190729023544.GA25930@compute1


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>