char/pcmcia: add scr24x_cs chip card interface driver

This implements only the very basic protocol "Mode A", just to make the
device functional. Patches to implement "Mode C" that uses better bulking
and is interrupt-driver may follow.

The device essentially speaks the same protocol as USB CCID devices do over
the bulk endpoints. The driver exchanges the command submissions and
responses over a plain read()/write() interface, compatible with legacy
OpenCT's pcmcia_block driver.

Patches for the newer CCID driver are available:
https://github.com/lkundrak/CCID/tree/lr/pcmcia_block

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>