Thank you for your investigation and fix! - for those who could not do the build themselves yet - here you can find my updated image (Armbian_5.77_Orangepi3_Ubuntu_bionic_dev_5.0.4_desktop.img) with this patch included - please report, if the emmc works with this image, as I did not have the opportunity to replace my own one, yet. - Thank you!
Edited 2019-03-30: private built file no longer available. You will be better off with the nightly builds from armbian from now on: https://dl.armbian.com/orangepi3/
Thanks to @martinayotte !
Frank Kettenbeil got a reaction from Slackstick in Orangepi 3 h6 allwiner chip