GPIO0 and GPIO1 are linked to unique interrupt line in PXA series,
others are linked to another interrupt line. All GPIO are linked to one
interrupt line in MMP series.

Since gpio driver is shared between PXA series and MMP series, define
GPIO0 and GPIO1 as chained interrupt chip. So we can move out gpio code
from irq.c to gpio-pxa.c.
Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>