ARM: 8595/2: apply more __ro_after_init

Guided by grsecurity's analogous __read_only markings in arch/arm,
this applies several uses of __ro_after_init to structures that are
only updated during __init.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>