mm/debug_vm_pgtables/hugevmap: use the arch helper to identify huge vmap support.

mm/debug_vm_pgtables/hugevmap: use the arch helper to identify huge vmap support.

ppc64 supports huge vmap only with radix translation.  Hence use arch
helper to determine the huge vmap support.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: 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/20200902114222.181353-5-aneesh.kumar@linux.ibm.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>