Restore eMMC HS400 on Helios64
signal integrity is not great at 200 MHz.
One of our board has
We also have some user reported issue (sometimes failed to initialized) with their eMMC even without HS400 mode and resolved with overlay that contains
max-frequency = 150000000
but this approach reduce the clock further that intended
use assigned-clock-rates property to reduce the clock and enable HS400 to compensate the lower clock.