ARM: pxa/colibri: don't register pxa2xx-pcmcia nodes on non-colibri platforms

PXA supports multi-machine kernels since long ago. However a kernel
compiled with support for colibri and any other PXA machine and with
PCMCIA enabled will barf at runtime about duplicate registration of
pxa2xx-pcmcia device. Fix that.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>