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/deviceinfo

@@ -13,7 +13,7 @@ deviceinfo_disable_dhcpd="true"
 # Device related
 deviceinfo_keyboard="true"
 deviceinfo_external_storage="true"
-deviceinfo_screen_width="800"
+deviceinfo_screen_width="1024"
 deviceinfo_screen_height="600"
 deviceinfo_dev_touchscreen=""
 deviceinfo_dev_touchscreen_calibration=""