ARM: pxa: mainstone: use new pxa_cplds driver

As the interrupt handling was transferred to the pxa_cplds driver,
make the switch in mainstone platform code.

Fixes: 157d2644 ("ARM: pxa: change gpio to platform device")
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Arnd Bergmann <arnd@arndb.de>