powerpc/mm: Fix build break with RADIX=y & HUGETLBFS=n
If we enable RADIX but disable HUGETLBFS, the build breaks with:
arch/powerpc/mm/pgtable-radix.c:557:7: error: implicit declaration of function 'pmd_huge'
arch/powerpc/mm/pgtable-radix.c:588:7: error: implicit declaration of function 'pud_huge'
Fix it by stubbing those functions when HUGETLBFS=n.
Fixes: 4b5d62ca17a1 ("powerpc/mm: add radix__remove_section_mapping()") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>