staging: comedi: remove unused CONFIG_COMEDI_PCMCIA define

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

Just remove it since the define is not used by any of the comedi
drivers.

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>