pageflag helpers for configed-out flags

Define proper false/noop inline functions for noreclaim page flags when
!defined(CONFIG_UNEVICTABLE_LRU)

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>