powerpc/book3s32: Reorder _PAGE_XXX flags to simplify TLB handling

For pages without _PAGE_USER, PP field is 00
For pages with _PAGE_USER, PP field is 10 for RW and 11 for RO.

This patch sets _PAGE_USER to 0x002 and _PAGE_RW to 0x001
is order to simplify TLB handling by reducing amount of shifts.

The location of _PAGE_PRESENT and _PAGE_HASHPTE doesn't matter
as they are only SW related flags.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>