mm: mlock_vma_pages_range() never return negative value

mm: mlock_vma_pages_range() never return negative value

Currently, mlock_vma_pages_range() never return negative value.  Then, we
can remove some worthless error check.

Signed-off-by: KOSAKI Motohiro <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Lee Schermerhorn <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>