linux-headers: bump 4.{14, 15}.x series

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/linux-headers/Config.in.host

@@ -248,6 +248,6 @@ config BR2_DEFAULT_KERNEL_HEADERS
 	default "4.11.12"	if BR2_KERNEL_HEADERS_4_11
 	default "4.12.14"	if BR2_KERNEL_HEADERS_4_12
 	default "4.13.16"	if BR2_KERNEL_HEADERS_4_13
-	default "4.14.17"	if BR2_KERNEL_HEADERS_4_14
-	default "4.15.1"	if BR2_KERNEL_HEADERS_4_15
+	default "4.14.18"	if BR2_KERNEL_HEADERS_4_14
+	default "4.15.2"	if BR2_KERNEL_HEADERS_4_15
 	default BR2_DEFAULT_KERNEL_VERSION if BR2_KERNEL_HEADERS_VERSION