allen_key

You can't. You have to wait until is fixed, donate that we will be able to hire help or fix on your own ... which will be much faster.  You can also switch to DEV kernel branch, which should be the same as it was before your upgrade. 
 
And remember, nightly kernels comes without support. If they break, nobody will fix them on the spot.

Yes...+1 to what Igor said...  Unfortunately as much as I wished wasn't the case I don't have any spare time to help with this currently...  My advice right now is that you take a look at my overlay additions for these two overlays (in the DEV branch now) - they are very small - and you could try manually building them for your 4.14 kernel.  This should be fairly straightforward (e.g., take a look at "armbian-add-overlay" on-device).  I hope this helps - good luck!

I have done a simple openssl benchmark for Allwinner H5 @ 816Mhz vs 1296MHz.
Just for all your information, I saw huge performance improvement @ 1296MHz.
 
Command: openssl speed -elapsed -evp aes-128-cbc
 
Thanks, 5kft bring us such useful information again.