Merge pull request #521 from stewart-ibm/bump-openpower-p9-skiboot

openpower_p9_mambo_defconfig: bump skiboot to include latest P9 patches
diff --git a/openpower/configs/openpower_p9_mambo_defconfig b/openpower/configs/openpower_p9_mambo_defconfig
index 6ed22b8..0701eb1 100644
--- a/openpower/configs/openpower_p9_mambo_defconfig
+++ b/openpower/configs/openpower_p9_mambo_defconfig
@@ -43,4 +43,4 @@
 BR2_PACKAGE_PETITBOOT=y
 # BR2_PACKAGE_OCC is not set
 BR2_SKIBOOT_CUSTOM_VERSION=y
-BR2_SKIBOOT_CUSTOM_VERSION_VALUE="8c2f3fe5639b1fbdd1aa3b13552d9666ecd81d05"
+BR2_SKIBOOT_CUSTOM_VERSION_VALUE="281e152366d461faf70f29b52bd7c892e24c7b5d"