pstore/ram: Adjust module param permissions to reflect reality

A couple module parameters had 0600 permissions, but changing them would
have no impact on ramoops, so switch these to 0400 to reflect reality.

Link: https://lore.kernel.org/lkml/20200506211523.15077-7-keescook@chromium.org/


Signed-off-by: Kees Cook <keescook@chromium.org>