Bump buildroot to 2019.02

bsp/buildroot/board/asus/tinker/readme.txt

@@ -0,0 +1,37 @@
+Tinker RK3288
+=============
+
+Tinker Board is a Single Board Computer (SBC) in an ultra-small form
+factor that offers class-leading performance while leveraging outstanding
+mechanical compatibility.
+
+Tinker link:
+https://www.asus.com/in/Single-Board-Computer/Tinker-Board/
+
+Wiki link:
+https://openedev.amarulasolutions.com/display/ODWIKI/Tinker+RK3288
+
+How to build it
+===============
+
+  $ make asus_tinker_rk3288_defconfig
+
+Then you can edit the build options using
+
+  $ make menuconfig
+
+Compile all and build rootfs image:
+
+  $ make
+
+Prepare your SDCard
+===================
+
+Buildroot generates a ready-to-use SD card image that you can flash directly to
+the card. The image will be in output/images/sdcard.img.
+You can write this image directly to an SD card device (i.e. /dev/xxx):
+
+  $ sudo dd if=output/images/sdcard.img of=/dev/xxx
+  $ sudo sync
+
+Finally, you can insert the SD card to the Tinker RK3288 board and boot it.