Update buildroot to 2015.05 base

Adds petitboot to openpower overlay rather rather than in buildroot branch.

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/openpower/package/Config.in b/openpower/package/Config.in
index 92ab00f..ab00242 100644
--- a/openpower/package/Config.in
+++ b/openpower/package/Config.in
@@ -6,6 +6,7 @@
 source "$BR2_EXTERNAL/package/firestone-xml/Config.in"
 source "$BR2_EXTERNAL/package/garrison-xml/Config.in"
 source "$BR2_EXTERNAL/package/openpower-pnor/Config.in"
+source "$BR2_EXTERNAL/package/petitboot/Config.in"
 source "$BR2_EXTERNAL/package/p8-pore-binutils/Config.in"
 source "$BR2_EXTERNAL/package/occ/Config.in"
 source "$BR2_EXTERNAL/package/capp-ucode/Config.in"