mm: fix fatal kernel-doc error

Fix a fatal kernel-doc error due to a #define coming between a function's
kernel-doc notation and the function signature.  (kernel-doc cannot handle
this)

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>