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="f462e07c7f3795f80b7f97ae0c6745d0807680dc021a866fd0450a0f17535efdaec2a19a5907a44d440b1bb870515db233824096a757c3b4a7b93ec354736a54  deviceinfo
-fc71acf937691b09f2ac9b8cd724af245555c90fdff6a1fd0e64c0cad04cfc0b46ff5dec61b3ff42e6b076b02e5cf2518089c54340c35a91c0b2b88731826492  uboot-script.cmd"
+995c26ac0422f3c9067f23e0cdd5bee004de18836a316337ffc359c379c51caae841deea3e185ea0e1fb61eab30639fe5155d2d3beea4ee9550aa0a8788da27f  uboot-script.cmd"