staging: iio: meter: remove fixme comment on device remove

This comment was in place in the original drafts of these drivers
when the remove function did a whole lot of work: flushed queues,
unregistered interrupts, uninitialized rings, unconfigured rings,
and a few kfree's.

The remove functions have since been reduced to unregistering and
stopping the device.  This is the inverse of what was done during
probe and is correct. Time to remove the comment.

Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Acked-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>