Bump buildroot to 2019.02

bsp/buildroot/board/bananapi/bananapi-m2-ultra/readme.txt

@@ -0,0 +1,35 @@
+Intro
+=====
+
+This default configuration will allow you to start experimenting with the
+buildroot environment for the Bananapi M2 ULtra. With the current
+configuration it will bring-up the board, and allow access through the
+serial console.
+
+Bananapi M2 Ultra link:
+http://www.banana-pi.org/m2u.html
+
+This configuration uses U-Boot mainline and kernel mainline.
+
+How to build
+============
+
+    $ make bananapi_m2_ultra_defconfig
+    $ make
+
+Note: you will need access to the internet to download the required
+sources.
+
+How to write the SD card
+========================
+
+Once the build process is finished you will have an image called "sdcard.img"
+in the output/images/ directory.
+
+Copy the bootable "sdcard.img" onto an SD card with "dd":
+
+  $ sudo dd if=output/images/sdcard.img of=/dev/sdX
+  $ sudo sync
+
+Insert the micro SDcard in your Bananapi M2 Ultra and power it up. The console
+is on the serial line, 115200 8N1.