arm64: dts: rockchip: add gpio-line-names to rk3308-rock-pi-s

Add names to the pins of the general-purpose expansion header as given in the
Radxa GPIO page[1] following the conventions in the kernel documentation[2] to
make it easier for users to correlate the pins with functions when using
utilities such as gpioinfo.

[1] https://wiki.radxa.com/RockpiS/hardware/gpio


[2] Documentation/devicetree/bindings/gpio/gpio.txt

Signed-off-by: Trevor Woerner <twoerner@gmail.com>
Link: https://lore.kernel.org/r/20231120162232.27653-1-twoerner@gmail.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>