configs/warp7: Bump kernel version

Bump kernel version to 4.15.15.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/warp7_defconfig

@@ -3,8 +3,8 @@ BR2_arm=y
 BR2_cortex_a7=y
 BR2_ARM_FPU_NEON_VFPV4=y
 
-# Linux headers same as kernel, a 4.12 series
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_12=y
+# Linux headers same as kernel, a 4.15 series
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_15=y
 
 # system
 BR2_TARGET_GENERIC_GETTY_PORT="ttymxc0"
@@ -15,7 +15,7 @@ BR2_ROOTFS_OVERLAY="board/warp7/rootfs_overlay"
 # Kernel
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.12.3"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.15.15"
 BR2_LINUX_KERNEL_DEFCONFIG="imx_v6_v7"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y
 BR2_LINUX_KERNEL_INTREE_DTS_NAME="imx7s-warp"