gpio: tegra: drop tegra specific GPIO lockdep classes

Since commit e45d1c80 ("gpio: put GPIO IRQs into their own lock
class") and commit a0a8bcf4 ("gpiolib: irqchip: use different
lockdep class for each gpio irqchip") GPIO lib takes care of lockdep
classes. In fact, gpiochip_irq_map() overwrites the class anyway, so
the lockdep class set by the driver is useless. Remove it.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>