pcmcia: add driver for hx4700

This patch adds support for the HP iPAQ hx4700 to the existing
pxa2xx-pcmcia driver.

Signed-off-by: Paul Parsons <lost.distance@yahoo.com>
Cc: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>