powerpc/nohash: Remove {pte/pmd}_protnone()

Only book3s/64 selects ARCH_SUPPORTS_NUMA_BALANCING so
CONFIG_NUMA_BALANCING can't be selected on nohash targets.

Remove pte_protnone() and pmd_protnone().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/a50c1a19828a8eced82cbcc5c61754b667037d21.1695659959.git.christophe.leroy@csgroup.eu