DESC
remap_file_pages protection support: fixups to ppc32 bits
EDESC
From: Paul Mackerras <paulus@samba.org>

When I tried -mm4 on a ppc32 box, it hit a BUG because I hadn't excluded
_PAGE_FILE from the bits used for swap entries.  While looking at that I
realised that the pte_to_pgoff and pgoff_prot_to_pte macros were wrong for
4xx and 8xx (embedded) PPC chips, since they use
