arm64: dts: rockchip: Add overlay for the PCIe slot on RK3576 EVB1

arm64: dts: rockchip: Add overlay for the PCIe slot on RK3576 EVB1

Rockchip RK3576 EVB1 has an onboard PCIe slot (PCIe 2.1, x4 mechanically,
x1 electrically), but it shares pins and PHY with the only USB3 Type-A
port.

There is a physical switch next to the slot to transfer respective pins
connection from the USB3 port to the PCIe slot, but apart from flipping
the switch one must also disable the USB3 host controller to prevent it
from claiming the PHY before the PCIe slot can become usable.

Add an overlay to disable the USB3 host port and instead enable the
PCIe slot, along with its pin configs. The physical switch must still be
flipped to the "ON - PCIe1" position for this to work.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
Link: https://patch.msgid.link/20251202-evb1-pcie1-v2-1-810693b1b72f@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>