meta-phosphor: nuvoton-layer: add gpio-keys kernel feature

The phosphor-base.inc distro file enables the phosphor-gpio-keys
KERNEL_FEATURE. Add support for this feature to the linux-nuvoton recipe
via a bbappend in meta-phosphor's nuvoton layer.

Tested: Built and ran on NPCM750 EVB

Change-Id: Id957c6209ebb841fce2cdad1cc0790e0d58da60c
Signed-off-by: Benjamin Fair <benjaminfair@google.com>
diff --git a/meta-phosphor/nuvoton-layer/recipes-kernel/linux/linux-nuvoton_%.bbappend b/meta-phosphor/nuvoton-layer/recipes-kernel/linux/linux-nuvoton_%.bbappend
new file mode 100644
index 0000000..71e208c
--- /dev/null
+++ b/meta-phosphor/nuvoton-layer/recipes-kernel/linux/linux-nuvoton_%.bbappend
@@ -0,0 +1,4 @@
+FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+
+SRC_URI += "file://phosphor-gpio-keys.scc"
+SRC_URI += "file://phosphor-gpio-keys.cfg"