Radxa Cubie A5E (1GB variant) fails to boot

[xunicatt]

The latest release version v15.1.1 for some reason fails to boot on my Radxa Cubie A5E with 1GB RAM. The vendor image boots and works fine.

[xunicatt]

@warpme The 1 GB variant uses different DRAM parameters. I couldn't get Armbian to boot until I discovered that this was the cause. Applying the following fix resolved the issue.

Here is the commit.