arm64: dts: rockchip: add enable-strobe-pulldown to emmc phy on nanopi4

Internal pull-down for strobe line (GRF_EMMCPHY_CON2[9]) was disabled
by commit 8b5c2b4, which causes I/O error in HS400 mode.

Tested on NanoPC-T4.

Fixes: 8b5c2b4 ("phy: rockchip: set pulldown for strobe line in dts")
Signed-off-by: Jensen Huang <jensenhuang@friendlyarm.com>
Link: https://lore.kernel.org/r/20220928091129.20597-1-jensenhuang@friendlyarm.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi

@@ -167,6 +167,7 @@
 };
 
 &emmc_phy {
+	rockchip,enable-strobe-pulldown;
 	status = "okay";
 };