kernel: enable KERNEL_DANGLING_FEATURES_WARN_ONLY

Uptream yocto recently added some new code which enforces
kernel feature validation. The commit which did this is:
https://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=095175595d9f28d5a0eb7ea520c9af0100bb8dfd

This caused OpenBMC builds to start failing with the following:
| ERROR: Feature 'phosphor-wdt-on-panic' not found, this will cause configuration failures.
| ERROR: Check the SRC_URI for meta-data repositories or directories that may be missing
| ERROR: Set KERNEL_DANGLING_FEATURES_WARN_ONLY to ignore this issue

OpenBMC does not utilize this aspect of the kernel-yocto.bbclass
so make it a warning only.

Tested:
Verified that the resultant build still had the expected CONFIG
options set in the linux-aspeed defconfig.

Resolves openbmc/openbmc#3690

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I605d65e888083aaec44af42129ceea0228ee0206
diff --git a/aspeed-layer/recipes-kernel/linux/linux-aspeed_%.bbappend b/aspeed-layer/recipes-kernel/linux/linux-aspeed_%.bbappend
index ea70a4f..6acd6a6 100644
--- a/aspeed-layer/recipes-kernel/linux/linux-aspeed_%.bbappend
+++ b/aspeed-layer/recipes-kernel/linux/linux-aspeed_%.bbappend
@@ -9,3 +9,10 @@
 
 KERNEL_FEATURES_append = " phosphor-vlan"
 KERNEL_FEATURES_remove_qemuall = " phosphor-vlan"
+
+python () {
+    # OpenBMC loads in kernel features via other mechanisms so this check
+    # in the kernel-yocto.bbclass is not required
+    d.setVar("KERNEL_DANGLING_FEATURES_WARN_ONLY","1")
+}
+