staging: comedi: split out PCMCIA support into new module

staging: comedi: split out PCMCIA support into new module

Setting the `CONFIG_COMEDI_PCMCIA_DRIVERS` kernel configuration option
makes the main "comedi" module depend on the "pcmcia" module, but many
machines don't have PCMCIA slots and only a few low-level Comedi drivers
need PCMCIA support.  The Comedi PCMCIA support functions are all in
"comedi_pcmcia.c".  Turn it into a separate module so we don't have to
pull in the other PCMCIA support modules unnecessarily.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>