pinctrl-tegra: Add config property GPIO mode

pinctrl-tegra: Add config property GPIO mode

The SFIO/GPIO select bit is a crucial part of Tegra's pin multiplexing
system:
- When set to 1, the pin operates in SFIO mode, controlled by the
  pin's assigned special function.
- When set to 0, the pin operates as a general-purpose GPIO.

This SFIO/GPIO select bit that is set for a given pin is not displayed,
adding the support to retrieve this information from the
pinmux set for each pin.

Signed-off-by: Prathamesh Shete <pshete@nvidia.com>
Link: https://lore.kernel.org/20241217153249.5712-1-pshete@nvidia.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>