staging: comedi: comedi_fops: do not call blocking ops when !TASK_RUNNING

commit cef988642cdac44e910a27cb6e8166c96f86a0df upstream.

Comedi's read and write file operation handlers (`comedi_read()` and
`comedi_write()`) currently call `copy_to_user()` or `copy_from_user()`
whilst in the `TASK_INTERRUPTIBLE` state, which falls foul of the
`might_fault()` checks when enabled.  Fix it by setting the current task
state back to `TASK_RUNNING` a bit earlier before calling these
functions.

Reported-by: Piotr Gregor <piotrgregor@rsyncme.org>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>