mm/debug_vm_pgtable/hugetlb: disable hugetlb test on ppc64

The seems to be missing quite a lot of details w.r.t allocating the
correct pgtable_t page (huge_pte_alloc()), holding the right lock
(huge_pte_lock()) etc.  The vma used is also not a hugetlb VMA.

ppc64 do have runtime checks within CONFIG_DEBUG_VM for most of these.
Hence disable the test on ppc64.

[anshuman.khandual@arm.com: drop hugetlb_advanced_tests()]
  Link: https://lore.kernel.org/lkml/289c3fdb-1394-c1af-bdc4-5542907089dc@linux.ibm.com/#t
  Link: https://lkml.kernel.org/r/1600914446-21890-1-git-send-email-anshuman.khandual@arm.com



Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lkml.kernel.org/r/20200902114222.181353-13-aneesh.kumar@linux.ibm.com


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