mm/thp/migration: switch from flush_tlb_range to flush_pmd_tlb_range

We remove one instace of flush_tlb_range here.  That was added by commit
f714f4f2

 ("mm: numa: call MMU notifiers on THP migration").  But the
pmdp_huge_clear_flush_notify should have done the require flush for us.
Hence remove the extra flush.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>