mm: Add folio flag manipulation functions

These new functions are the folio analogues of the various PageFlags
functions.  If CONFIG_DEBUG_VM_PGFLAGS is enabled, we check the folio
is not a tail page at every invocation.  This will also catch the
PagePoisoned case as a poisoned page has every bit set, which would
include PageTail.

This saves 1684 bytes of text with the distro-derived config that
I'm testing due to removing a double call to compound_head() in
PageSwapCache().

Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Acked-by: Jeff Layton <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Reviewed-by: William Kucharski <[email protected]>
Reviewed-by: David Howells <[email protected]>
Acked-by: Mike Rapoport <[email protected]>