The following three changes have been added to provide initial Power11 support.
1. Add the directories to hold Power11 files.
2. Add support to select Power11 libraries based on AT_PLATFORM.
3. Let submachine=power11 be set automatically.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Peter Bergner <bergner@linux.ibm.com>