powerpc: Remove pte_mkuser() and pte_mkpriviledged()

pte_mkuser() is never used. Remove it.

pte_mkpriviledged() is not used anymore. Remove it too.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/1a1dc18816456c637dc8a9c38d532f7598b60ac4.1695659959.git.christophe.leroy@csgroup.eu