powerpc/64s: move page size definitions from hash specific file

The radix code uses some of the psize variables. Move the common
ones from hash_utils.c to pgtable.c.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211201144153.2456614-10-npiggin@gmail.com