powerpc/mm: Remove the debug hugepd_ok check

We don't do this for other page table entries. So lets keep this simple
and always return false for hugepd check on a 64K page size config.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>