dt-bindings: gpio: Add Tegra256 support

dt-bindings: gpio: Add Tegra256 support

Extend the existing Tegra186 GPIO controller device tree bindings with
support for the GPIO controller found on Tegra256. The number of pins is
slightly different, but the programming model remains the same

Add a new header, include/dt-bindings/gpio/tegra256-gpio.h,
that defines port IDs as well as the TEGRA256_MAIN_GPIO() helper,
both of which are used in conjunction to create a unique specifier
for each pin. The OS can reconstruct the port ID and pin from
these values to determine the register region for the corresponding
GPIO. However, the OS does not use the macro definitions in this file.

The symbolic names help associate these GPIO specifiers with the names
used in the technical documentation available for the chip.

Signed-off-by: Prathamesh Shete <pshete@nvidia.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250823055420.24664-1-pshete@nvidia.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>