Initial PINE A64-LTS support

Here's my WIP branch for the PINE A64-LTS, mainline u-boot crashes before starting the kernel:

U-Boot SPL 2018.05 (Sep 08 2018 - 15:35:14 +0000)
DRAM: 0 MiB
### ERROR ### Please RESET the board ###

This branch also depends on https://gitlab.com/postmarketOS/pmbootstrap/merge_requests/1693

device/device-pine-a64lts/APKBUILD

@@ -27,4 +27,4 @@ package() {
 }
 
 sha512sums="8891ab307e9e2272ae250c1d3b20900c44c433513ac2dd3abeb01de042e26844fea264f15024312c3447931643e828f9f2c8e06905e91a31e1bb38143f8135c0  deviceinfo
-e9ce432acbb455929be2f61cda7605110b16f0a9ed7bce07624a11974bf9b8a498528c23aa6536ec2ad6a60330faf9b8627a81428b98491a7477d30d6e444163  uboot-script.cmd"
+cf75389c3b795014577b41dcd69ef29bbc38881a4f147a4e18e8652a5b8b0362ce60481cdc9129497af494937e8acc87c621ee5d484367ee22045b10197efe1b  uboot-script.cmd"