mm/swap: comment all the ifdef in swapops.h

swapops.h contains quite a few layers of ifdef, some of the "else" and
"endif" doesn't get proper comment on the macro so it's hard to follow on
what are they referring to.  Add the comments.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Peter Xu <[email protected]>
Suggested-by: Nadav Amit <[email protected]>
Reviewed-by: Huang Ying <[email protected]>
Reviewed-by: Alistair Popple <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Dave Hansen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions