staging: comedi: conditionally build in PCMCIA driver support

Separate the comedi_pcmcia_* functions out of drivers.c into a new
source file, comedi_pcmcia.c. This allows conditionally building
support for comedi pcmcia drivers into the comedi core without the
need for the #if'defery. Fix the Kconfig and Makefile appropriately.

Group all the comedi_pcmcia_* prototypes into one place in comedidev.h.
Protect these prototypes with an #ifdef so that building a comedi
pcmcia driver without PCMCIA support will cause a build error. This
will normally not happen as long as the comedi pcmcia driver is placed
in the proper group in the Kconfig.

Remove the #include <pcmcia/*.h> from drivers.c. These includes are only
needed by the comedi pcmcia driver support code and the pcmcia drivers.
The include should occur in those files.

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>