ARM: tegra2: convert to CONFIG_MULTI_IRQ_HANDLER

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: Stephen Warren <swarren@nvidia.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>