mm, hugetlb: remove decrement_hugepage_resv_vma()

mm, hugetlb: remove decrement_hugepage_resv_vma()

Now, Checking condition of decrement_hugepage_resv_vma() and
vma_has_reserves() is same, so we can clean-up this function with
vma_has_reserves().  Additionally, decrement_hugepage_resv_vma() has only
one call site, so we can remove function and embed it into
dequeue_huge_page_vma() directly.  This patch implement it.

Signed-off-by: Joonsoo Kim <[email protected]>
Reviewed-by: Wanpeng Li <[email protected]>
Reviewed-by: Aneesh Kumar K.V <[email protected]>
Acked-by: Hillf Danton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: "Aneesh Kumar K.V" <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: David Gibson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>