pinctrl: tegra: Set specific GPIO compatible string

Rather than reuse the nvidia,tegra30-gpio compatible string
to find the GPIO controller on Tegra30, Tegra114, Tegra124 and
Tegra210, use the most specific compatible string for each
SoC generation for consistency.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>