powerpc/32s: Activate KUAP and KUEP by default

Now that KUAP and KUEP have been significantly optimised and can be
disabled at boot time using 'nosmap' and 'nosmep' kernel parameters,
them can be active by default like in other powerpc platforms.

It is still possible to disable them completely in the configuration.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/86c7c74a3ba5312daea7e9658b096e2bcc6f4b64.1622708530.git.christophe.leroy@csgroup.eu