powerpc/mm: Remove radix dependency on HugeTLB page

Now that we have switched the page table walk to use pmd_is_leaf we can now
revert commit 8adddf34 ("powerpc/mm/radix: Make Radix require HUGETLB_PAGE")

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