rk3318: enable rng-seed population in u-boot

[alex3d]

Description

Enable rng-seed population in u-boot. This significantly speeds-up encrypted overlayroot mount (by 5 sec or so), and I expect cryptroot would benefit either.

Without patch:

# dmesg | grep crng
[   12.089286] random: crng init done

With patch:

# dmesg | grep crng
[    0.000000] random: crng init done

How Has This Been Tested?

• Build and run rk3318-box

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code

[alex3d]

cc @paolosabatino

[paolosabatino]

Cool, thanks!