gpio: tegra: configure pins during irq_set_type

When a Tegra GPIO is used as an IRQ, it should be enabled as a GPIO (so
the pinmux module isn't driving it as an output) and configured as a GPIO
input (so the GPIO module isn't driving it as an output). Set this up
automatically whenever an IRQ is requested, so that users of IRQs don't
need to do this.

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