ARM: dts: pxa910: Fix the gpio interrupt cell number

gpio-pxa uses two cell to encode the interrupt source: the pin number
and the trigger type. Adjust the device node accordingly.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>