staging: comedi: use EXPORT_SYMBOL_GPL() for all exported symbols

Comedi is licensed under GPL. Some if its exports are currently
EXPORT_SYMBOL() and others are EXPORT_SYMBOL_GPL(). Change them all
to EXPORT_SYMBOL_GPL() and see if anyone reports any fall out.

If any of the symbols "need" to be EXPORT_SYMBOL() they will be
addressed as needed.

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>