mm/debug_vm_pgtable/pmd_clear: don't use pmd/pud_clear on pte entries

pmd_clear() should not be used to clear pmd level pte entries.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lkml.kernel.org/r/20200902114222.181353-12-aneesh.kumar@linux.ibm.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>