rockchip: rk3568-generic: Enable eMMC HS200 mode

Writing to eMMC using HS200 mode work more reliably then other modes on
RK356x boards.

Add device tree props and enable Kconfig options for eMMC HS200 mode on
the generic RK3566/RK3568 board. Also enable the pinctrl driver in SPL
and add missing rk3568-generic.dtb to Makefile.

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