powerpc/64s: Make mmu_hash_ops __ro_after_init

The mmu_hash_ops are only assigned to during boot, so mark them
__ro_after_init to prevent any further modification.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240821080745.872151-1-mpe@ellerman.id.au

Author: mpe

arch/powerpc/mm/book3s64/hash_utils.c

@@ -125,7 +125,7 @@ int mmu_ci_restrictions;
 #endif
 static u8 *linear_map_hash_slots;
 static unsigned long linear_map_hash_count;
-struct mmu_hash_ops mmu_hash_ops;
+struct mmu_hash_ops mmu_hash_ops __ro_after_init;
 EXPORT_SYMBOL(mmu_hash_ops);
 
 /*