staging: comedi: remove CONFIG_COMEDI_PCI define

CONFIG_COMEDI_PCI is not actually a Kconfig option. It is defined
in the comedidev.h header based on another Kconfig option being
enabled.

It is only referenced in the skel driver to conditionally compile
in the PCI support code. Use the CONFIG_COMEDI_PCI_DRIVERS Kconfig
option instead and remove the define.

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