Bump buildroot to 2019.02

bsp/buildroot/configs/qemu_riscv64_virt_defconfig

@@ -0,0 +1,24 @@
+# Architecture
+BR2_riscv=y
+BR2_RISCV_64=y
+
+# System
+BR2_SYSTEM_DHCP="eth0"
+
+# Filesystem
+BR2_TARGET_ROOTFS_EXT2=y
+BR2_TARGET_GENERIC_GETTY=y
+BR2_TARGET_GENERIC_GETTY_PORT="ttyS0"
+
+# Linux headers same as kernel, a 4.20 series
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_20=y
+
+# Kernel
+BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_GIT=y
+BR2_LINUX_KERNEL_CUSTOM_REPO_URL="https://github.com/riscv/riscv-linux.git"
+BR2_LINUX_KERNEL_CUSTOM_REPO_VERSION="8fe28cb58bcb235034b64cbbb7550a8a43fd88be"
+BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG=y
+
+# Bootloader
+BR2_TARGET_RISCV_PK=y