VESNIN: Bump kernel version from 4.15.6 to 4.15.9

Signed-off-by: Artem Senichev <a.senichev@yadro.com>
diff --git a/openpower/configs/vesnin_defconfig b/openpower/configs/vesnin_defconfig
index 0425d18..8603451 100644
--- a/openpower/configs/vesnin_defconfig
+++ b/openpower/configs/vesnin_defconfig
@@ -12,7 +12,7 @@
 BR2_ROOTFS_POST_BUILD_SCRIPT="../openpower/scripts/fixup-target-var ../openpower/scripts/firmware-whitelist"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.15.6"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.15.9"
 BR2_LINUX_KERNEL_PATCH="$(BR2_EXTERNAL_OP_BUILD_PATH)/linux"
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
 BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="$(BR2_EXTERNAL_OP_BUILD_PATH)/configs/linux/skiroot_defconfig"