gpio: add interrupt handling capability to max732x

Most of the GPIO expanders supported by the max732x driver have interrupt
generation capability by reporting changes on input pins through an INT#
pin.  This patch implements the irq_chip functionnality (edge detection
only).

Signed-off-by: Marc Zyngier <maz@misterjones.org>
Cc: Eric Miao <eric.y.miao@gmail.com>
Cc: Jebediah Huang <jebediah.huang@gmail.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/i2c/max732x.h b/include/linux/i2c/max732x.h
index e103366..c04bac8 100644
--- a/include/linux/i2c/max732x.h
+++ b/include/linux/i2c/max732x.h
@@ -7,6 +7,9 @@
 	/* number of the first GPIO */
 	unsigned	gpio_base;
 
+	/* interrupt base */
+	int		irq_base;
+
 	void		*context;	/* param to setup/teardown */
 
 	int		(*setup)(struct i2c_client *client,