staging: comedi: Makefile: conditionally compile multi-file core module

Instead of using the #ifdef'ery in the comedi_compat32.c and proc.c
files to include/exclude them from the comedi core, modify the Makefile
to include those files automatically when enabled in the .config.

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>