orangepi-zero: bump linux to 4.15, u-boot to 2018.01

And enable dhcp for eth0 now that the ethernet is finally supported.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/orangepi_zero_defconfig

@@ -3,12 +3,13 @@ BR2_cortex_a7=y
 BR2_ARM_FPU_VFPV4=y
 BR2_GLOBAL_PATCH_DIR="board/orangepi/orangepi-zero/patches"
 BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV=y
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_13=y
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_15=y
 BR2_TARGET_GENERIC_HOSTNAME="OrangePi_Zero"
 BR2_TARGET_GENERIC_ISSUE="Welcome to Buildroot for the Orange Pi Zero"
+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-h2-plus-orangepi-zero"
@@ -19,7 +20,7 @@ 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_zero"
 BR2_TARGET_UBOOT_NEEDS_DTC=y
 BR2_TARGET_UBOOT_FORMAT_CUSTOM=y