powerpc/8xx: simplify struct mmu_psize_def

powerpc/8xx: simplify struct mmu_psize_def

On 8xx, only the shift field is used in struct mmu_psize_def

Remove other fields and related macros.

Link: https://lkml.kernel.org/r/dd0587a9e8354005858c7f8c9a775ad05523b314.1719928057.git.christophe.leroy@csgroup.eu
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>