linux-phytec-ti

powerpc/mm: Add virt_to_pfn and use this instead of opencoding

This add helper virt_to_pfn and remove the opencoded usage of the
same.

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