rockchip: dts: rk3399: nanopi4: Use CD pin as RK_FUNC_1

Attaching GPIO functionality to SDMMC0_DET pin (which
does in Linux base dts) make dwmmc driver "fail to detect
the card".

  Card did not respond to voltage select!

It may be because the existing driver can't support gpio
card detection. So, change the pinctrl functionality from
RK_FUNC_GPIO to RK_FUNC_1 like other rk3399 dts does via
sdmmc_cd pin.

Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>