arm: dts: rockchip: Fix eMMC write on RK3528

arm: dts: rockchip: Fix eMMC write on RK3528

Writing to eMMC on RK3528 is affected with the same or a similar issue
as on RK3588, where eMMC must init to HS200 at least once to fully work.

Trying to write u-boot-rockchip.bin to eMMC fails with:

  => mmc write $fileaddr 40 5000
  MMC write: dev # 0, block # 64, count 20480 ... mmc write failed
  0 blocks written: ERROR

For U-Boot to enable HS200 mode the mmc-hs200-1_8v prop must be defined
in the device tree. Linux does not seem to be affected and is able to
detect and use HS200 without this prop.

Enable use of HS200 and fix eMMC write on RK3528 by adding the missing
mmc-hs200-1_8v prop for affected boards:

  => mmc write $fileaddr 40 5000
  MMC write: dev # 0, block # 64, count 20480 ... 20480 blocks written: OK

Fixes: b112a44531cb ("board: rockchip: Add minimal generic RK3528 board")
Fixes: ccbddf645310 ("board: rockchip: Add Radxa E20C")
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>