staging: comedi: comedi_fops: move comedi_cleanup_legacy_minors()

This function is only called by the module_{init,exit} functions. For
aesthetic reasons, move it near them.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>