The generic hugetlbfs code can handle not finding the default huge page
size correctly. With HPAGE_SHIFT = 0 we see in dmesg:

  hugetlbfs: disabling because there are no supported hugepage sizes

bash-4.2# echo 30 > /proc/sys/vm/nr_hugepages
bash: echo: write error: Operation not supported

Fixes: 03bb2d65 ("powerpc: get hugetlbpage handling more generic")
Reported-by: NChris Smart <chris@distroguy.com>
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>