Bump buildroot to 2019.02

bsp/buildroot/board/aarch64-efi/readme.txt

@@ -0,0 +1,34 @@
+
+The aarch64_efi_defconfig allows to build a minimal Linux system that
+can boot on all AArch64 servers providing an EFI firmware and ACPI.
+
+Building and booting
+====================
+
+$ make aarch64_efi_defconfig
+$ make
+
+The file output/images/disk.img is a complete disk image that can be
+booted, it includes the grub2 bootloader, Linux kernel and root
+filesystem.
+
+Testing under Qemu
+==================
+
+This image can also be tested using Qemu:
+
+qemu-system-aarch64 \
+	-M virt \
+	-cpu cortex-a57 \
+	-m 512 \
+	-nographic \
+	-bios </path/to/QEMU_EFI.fd> \
+	-drive file=output/images/disk.img,if=none,format=raw,id=hd0 \
+	-device virtio-blk-device,drive=hd0 \
+	-netdev user,id=eth0 \
+	-device virtio-net-device,netdev=eth0
+
+Note that </path/to/QEMU_EFI.fd> needs to point to a valid aarch64 UEFI
+firmware image for qemu.
+It may be provided by your distribution as a edk2-aarch64 or AAVMF
+package, in path such as /usr/share/edk2/aarch64/QEMU_EFI.fd .