ARM: tegra: Remove use of TEGRA_GPIO_TO_IRQ

Replace compile-time usage of TEGRA_GPIO_TO_IRQ with run-time calls to
gpio_to_irq(). This will allow the base IRQ number for the Tegra GPIO
driver to be dynamically allocated in a later patch.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Olof Johansson <olof@lixom.net>