ARM: dts: rockchip: Fix sdmmc_pwren's pinmux setting for RK3128

[ Upstream commit 0c349b50 ]

RK3128's reference design uses sdmmc_pwren pincontrol as GPIO - see [0].

Let's change it in the SoC DT as well.

[0] https://github.com/rockchip-linux/kernel/commit/8c62deaf6025

Fixes: a0201bff

 ("ARM: dts: rockchip: add rk3128 soc dtsi")
Signed-off-by: Alex Bee <knaerzche@gmail.com>
Link: https://lore.kernel.org/r/20231127184643.13314-2-knaerzche@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>