powerpc/hugetlb: Call mm_dec_nr_pmds() in hugetlb_free_pmd_range()
powerpc/hugetlb: Call mm_dec_nr_pmds() in hugetlb_free_pmd_range()

Commit dc6c9a35b66b5 ("mm: account pmd page tables to the process")
added a counter that is incremented whenever a PMD is allocated and
decremented whenever a PMD is freed.  For hugepages on PPC, common code
is used to allocated PMDs, but arch-specific code is used to free PMDs.

This results in kernel output such as "BUG: non-zero nr_pmds on freeing
mm: 1" when using hugepages.

Update the PPC hugepage PMD freeing code to decrement the count, just
as the above commit did for free_pmd_range().

Fixes: dc6c9a35b66b5 ("mm: account pmd page tables to the process")
Signed-off-by: Scott Wood <b77916c2feab81a70245e7b5671f4f02730ebf64@freescale.com>
Reviewed-by: Aneesh Kumar K.V <f511f818e8a0748edef6b9ee378967da9ed0c78f@linux.vnet.ibm.com>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org # 4.0.x

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs