fsp2: move to 4.17.18

Bump the linux kernel version to 4.17.18 which includes
fix for the secuirity vulnerability in #3359.

Signed-off-by: Ivan Mikhaylov <ivan@de.ibm.com>
Change-Id: Ia09a7baada1a78a3e6b1186fe6fa015344db6048
diff --git a/meta-fsp2/recipes-kernel/linux/linux-fsp2.inc b/meta-fsp2/recipes-kernel/linux/linux-fsp2.inc
index 0f65dfe..23ecc45 100644
--- a/meta-fsp2/recipes-kernel/linux/linux-fsp2.inc
+++ b/meta-fsp2/recipes-kernel/linux/linux-fsp2.inc
@@ -4,7 +4,7 @@
 
 KCONFIG_MODE="--alldefconfig"
 
-KSRC ?= "git://github.com/openbmc/linux;protocol=git;branch=dev-4.13"
+KSRC ?= "git://github.com/openbmc/linux;protocol=git;branch=dev-4.17"
 SRC_URI = "${KSRC}"
 
 LINUX_VERSION_EXTENSION ?= "-${SRCREV}"