rockchip: rk3588-rock-5b: Add bootph prop to pinctrl for uart2 and sdhci

Enable pinctrl for sdhci in SPL to support loading of FIT image from SD
and eMMC storage when booting from SPI NOR flash.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>