Remove support for POWER8 targets

* Remove configurations and packages related to POWER8 machines
* Adjust documentation where relevant
* Move 'opal_defconfig' to use Power9

Signed-off-by: Nick Bofferding <bofferdn@us.ibm.com>
Signed-off-by: Klaus Heinrich Kiwi <klaus@linux.vnet.ibm.com>
diff --git a/openpower/package/openpower-pnor/Config.in b/openpower/package/openpower-pnor/Config.in
index 82280f5..6311b50 100644
--- a/openpower/package/openpower-pnor/Config.in
+++ b/openpower/package/openpower-pnor/Config.in
@@ -1,13 +1,11 @@
 config BR2_PACKAGE_OPENPOWER_PNOR
         bool "openpower_pnor"
         default y if (BR2_OPENPOWER_PLATFORM)
-        select BR2_PACKAGE_HOSTBOOT if !BR2_OPENPOWER_POWER8
-        select BR2_PACKAGE_HOSTBOOT_P8 if BR2_OPENPOWER_POWER8
+        select BR2_PACKAGE_HOSTBOOT
         select BR2_PACKAGE_HOSTBOOT_BINARIES
         select BR2_PACKAGE_SKIBOOT
         select BR2_PACKAGE_OPENPOWER_FFS
-        select BR2_PACKAGE_OCC if !BR2_OPENPOWER_POWER8
-        select BR2_PACKAGE_OCC_P8 if BR2_OPENPOWER_POWER8
+        select BR2_PACKAGE_OCC
         select BR2_PACKAGE_CAPP_UCODE
         select BR2_PACKAGE_IMA_CATALOG
         select BR2_PACKAGE_HOST_OPENPOWER_VPNOR