PCMCIA: fix pxa2xx_lubbock modular build error

ERROR: "pxa2xx_drv_pcmcia_ops" [drivers/pcmcia/pxa2xx_lubbock_cs.ko] undefined!
ERROR: "pxa2xx_drv_pcmcia_add_one" [drivers/pcmcia/pxa2xx_lubbock_cs.ko] undefined!

We also remove __pxa2xx_drv_pcmcia_probe and its export, since this is
no longer required.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>