Single XML package rather than one per platform

This saves us a *lot* of copy&pasted build foo and replaces it with a couple
of config options that can be set in menuconfig.

This makes adding a new platform a much smaller operation, requiring fewer
changes that are scattered throughout the buildroot tree.

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/openpower/configs/witherspoon_defconfig b/openpower/configs/witherspoon_defconfig
index 91868e9..aa393a2 100644
--- a/openpower/configs/witherspoon_defconfig
+++ b/openpower/configs/witherspoon_defconfig
@@ -43,7 +43,6 @@
 BR2_HOSTBOOT_CONFIG_FILE="witherspoon.config"
 BR2_OPENPOWER_PNOR_XML_LAYOUT_FILENAME="defaultPnorLayout_64.xml"
 BR2_OPENPOWER_CONFIG_NAME="witherspoon"
-BR2_OPENPOWER_XML_PACKAGE="witherspoon-xml"
 BR2_OPENPOWER_PNOR_FILENAME="witherspoon.pnor"
 BR2_OPENPOWER_PNOR_UPDATE_FILENAME="witherspoon_update.pnor"
 BR2_HOSTBOOT_BINARY_SBE_FILENAME="nimbus_sbe.img.ecc"
@@ -59,7 +58,13 @@
 BR2_SKIBOOT_CUSTOM_VERSION=y
 BR2_SKIBOOT_CUSTOM_VERSION_VALUE="f0ebbc8318e64870a68d337e77b0257678c2b055"
 BR2_PACKAGE_LOADKEYS=y
-BR2_WITHERSPOON_SYSTEM_XML_FILENAME="WITHERSPOON_hb.system.xml"
-BR2_WITHERSPOON_MRW_XML_FILENAME="WITHERSPOON_hb.mrw.xml"
-BR2_WITHERSPOON_BIOS_XML_FILENAME="WITHERSPOON_bios.xml"
+BR2_OPENPOWER_MACHINE_XML_PATCH="$(BR2_EXTERNAL_OP_BUILD_PATH)/package/machine-xml/witherspoon-patches"
+BR2_OPENPOWER_MACHINE_XML_GITHUB_PROJECT=y
+BR2_OPENPOWER_MACHINE_XML_GITHUB_PROJECT_VALUE="witherspoon-xml"
+BR2_OPENPOWER_MACHINE_XML_VERSION="cee25d28dfe368a1838a0ef9295d6652da851635"
+BR2_OPENPOWER_MACHINE_XML_FILENAME="witherspoon.xml"
+BR2_OPENPOWER_SYSTEM_XML_FILENAME="WITHERSPOON_hb.system.xml"
+BR2_OPENPOWER_MRW_XML_FILENAME="WITHERSPOON_hb.mrw.xml"
+BR2_OPENPOWER_BIOS_XML_FILENAME="WITHERSPOON_bios.xml"
 BR2_IMA_CATALOG_DTS="POWER9"
+BR2_GLOBAL_PATCH_DIR="$(BR2_EXTERNAL_OP_BUILD_PATH)/patches/witherspoon-patches"