arm64: dts: rockchip: Fix vcc_sdio regulator max voltage on Pinebook Pro

The vcc_sdio regulator supports 1.8V to 3.4V output range according to
its datasheet.

The current DT incorrectly limits the max voltage to 3.0V. This limit
causes issues issues downstream with u-boot, which refuses to apply the
out-of range value, and falls back to the minimum in that range: 1.8V.
This is insufficient to power the SD card, so driver initialisation
fails and booting from it does not work.

Set regulator-max-microvolt to 3400000 µV to match hardware capability.
This matches the rk3399-orangepi for the same regulator.

Signed-off-by: Hugo Osvaldo Barrera <hugo@whynothugo.nl>
Reviewed-by: Dang Huynh <dang.huynh@mainlining.org>
Link: https://patch.msgid.link/20260519094439.7918-1-hugo@whynothugo.nl
Signed-off-by: Heiko Stuebner <heiko@sntech.de>