powerpc/kuap: Wire-up KUAP on book3e/64

This adds KUAP support to book3e/64.
This is done by reading the content of SPRN_MAS1 and checking
the TID at the time user pgtable is loaded.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/e2c2c9375afd4bbc06aa904d0103a5f5102a2b1a.1634627931.git.christophe.leroy@csgroup.eu