arm64: dts: rockchip: remove ethm0_clk0_25m_out from Sige5 gmac0

arm64: dts: rockchip: remove ethm0_clk0_25m_out from Sige5 gmac0

The GPIO3 A4 pin on the ArmSoM Sige5 is routed to the 40-pin GPIO
header. This pin can serve a variety of functions, including ones of
questionable use to us on a GPIO header such as the 25MHz clock of the
ethernet controller.

Unfortunately, this is the precise function that it is being claimed for
by the gmac0 node in the Sige5 board dts, meaning it can't be used for
anything else despite serving no useful function in this role. Since it
goes through a RS0108 bidirectional voltage level translator with a
maximum data rate of 24Mbit/s in push-pull mode and 2Mbit/s data rate in
open-drain mode, it's doubtful as to whether the 25MHz clock signal
would even survive to the actual user-accessible pin it terminates in.

Remove it to leave the pin for users to play with. It's infinitely more
useful as a GPIO or even as a PWM.

Fixes: 40f742b07ab2 ("arm64: dts: rockchip: Add rk3576-armsom-sige5 board")
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Link: https://lore.kernel.org/r/20250314-rk3576-sige5-eth-clk-begone-v1-1-2858338fc555@collabora.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>