beaglebone-black: select upstream 4.14.x kernel by default

target/linux/Config.in.kernelversion

@@ -6,7 +6,6 @@ prompt "Linux Kernel version" if !ADK_TARGET_CHOOSE_ARCH
 depends on ADK_TARGET_OS_LINUX
 default ADK_TARGET_LINUX_KERNEL_VERSION_GIT if ADK_TARGET_BOARD_BCM28XX
 default ADK_TARGET_LINUX_KERNEL_VERSION_GIT if ADK_TARGET_SYSTEM_SOLIDRUN_CLEARFOG
-default ADK_TARGET_LINUX_KERNEL_VERSION_GIT if ADK_TARGET_SYSTEM_BEAGLEBONE_BLACK
 default ADK_TARGET_LINUX_KERNEL_VERSION_GIT if ADK_TARGET_SYSTEM_KINETIS_K70
 default ADK_TARGET_LINUX_KERNEL_VERSION_GIT if ADK_TARGET_SYSTEM_ADSP_BF537
 default ADK_TARGET_LINUX_KERNEL_VERSION_GIT if ADK_TARGET_SYSTEM_PHYTEC_WEGA