staging: comedi: ni_labpc: remove forward declarations 1

Move the comedi_driver (*attach), (*auto_attach), and (*detach)
functions as well as a couple of the attach helper functions to
remove the need for a number of the forward declarations.

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