orangepi-one: bump kernel and u-boot versions

Bump Linux to 4.15 and U-Boot to 2018.01. Enable dhcp for eth0 since
Ethernet support for Allwinner H2/H3 SoCs has landed in Linux 4.15.

Signed-off-by: Sergey Matyukevich <geomatsi@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/orangepi_one_defconfig

@@ -1,12 +1,13 @@
 BR2_arm=y
 BR2_cortex_a7=y
 BR2_ARM_FPU_VFPV4=y
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_13=y
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_15=y
 BR2_TARGET_GENERIC_HOSTNAME="OrangePi_One"
 BR2_TARGET_GENERIC_ISSUE="Welcome to Buildroot for the Orange Pi One"
+BR2_SYSTEM_DHCP="eth0"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.13.11"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.15"
 BR2_LINUX_KERNEL_DEFCONFIG="sunxi"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y
 BR2_LINUX_KERNEL_INTREE_DTS_NAME="sun8i-h3-orangepi-one"
@@ -16,7 +17,7 @@ BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
-BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2017.09"
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2018.01"
 BR2_TARGET_UBOOT_BOARD_DEFCONFIG="orangepi_one"
 BR2_TARGET_UBOOT_NEEDS_DTC=y
 BR2_TARGET_UBOOT_FORMAT_CUSTOM=y