bcma: gpio: use ChipCommon GPIO IRQ on BCM47XX arch only

GPIOs can be also used on bcm53xx, however this arch requires different
implementation of IRQ support. It uses different IRQ number (117) and
different masks & acking.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>