Bump buildroot to 2019.02

bsp/buildroot/board/lego/ev3/readme.txt

@@ -70,6 +70,13 @@ official Lego Mindstorms EV3 programming software firmware update tool to load
 the image. To use sdcard.img, use a disk writing tool such as Etcher or dd to
 write the image to the µSD card.
 
+NOTE: The sdcard.img created by lego_ev3_defconfig won't boot if the official
+LEGO firmware is installed on the EV3 (it has an old version of U-Boot that
+doesn't know about device tree). You must either set the kernel configuration
+option to append the device tree to the kernel or you can create a boot.scr
+that chainloads a newer U-Boot or you can install a newer U-Boot in the flash
+memory (just flashing u-boot.bin is enough).
+
 Finish
 ======
 
@@ -80,3 +87,13 @@ See:
 - http://botbench.com/blog/2013/08/05/mindsensors-ev3-usb-console-adapter/
 
 The serial port config to use is 115200/8-N-1.
+
+Bluetooth
+=========
+
+To enable Bluetooth:
+
+    # modprobe hci_uart
+    # /usr/libexec/bluetooth/bluetoothd &
+    # bluetoothctl
+    [bluetooth]# power on