gpio: tegra: Remove unnecessary check

of_device_get_match_data() can never return NULL, therefore the check
for NULL values is unnecessary.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>