Convert the tegra2 platforms to be using the gic_handle_irq
function as their primary interrupt handler.

Tested on harmony.

Cc: Colin Cross <ccross@android.com>
Acked-by: NStephen Warren <swarren@nvidia.com>
Acked-by: NOlof Johansson <olof@lixom.net>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>