[POWERPC] Schedule removal of arch/ppc

The arch/ppc tree has been in a semi-nebulous "bug fix only" state for a
few kernel releases now.  The patch below officially declares this as of
the 2.6.22 kernel release and schedules arch/ppc for removal in June of
2008.

Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>