powerpc/32: Remove __map_without_ltlbs

__map_without_ltlbs is used only for 40x, and only when
STRICT_KERNEL_RWX, KFENCE or DEBUG_PAGEALLOC is active.

Do the verification directly in 40x version of mmu_mapin_ram()
and remove __map_without_ltlbs from core ppc32.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/3422094db965d218c4c3d8580f526963a9ac897f.1655202721.git.christophe.leroy@csgroup.eu