PCMCIA: fix pxa2xx_lubbock modular build error

Commit d0d26c33

 broke the driver by
propagating a pointer to the platform_device where a pointer to the
generic device was expected, leading to a spectacular crash...

Signed-off-by: Marc Zyngier <maz@misterjones.org>
Acked-by: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Eric Miao <eric.y.miao@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>