ARM: 9389/2: mm: Define prototypes for all per-processor calls

Each CPU type ("proc") has assembly calls for initializing and
setting up the MM context, idle and so forth.

These calls have the C form of e.g.:

void cpu_arm920_init(void);

However this prototype is not really specified, instead it is
generated by the glue code in <asm/glue-proc.h> and the prototype
is implicit from the generic prototype defined in <asm/proc-fns.h>
such as cpu_proc_init() in this case. (This is a bit similar to
the "interface" or inheritance concept in other languages.)

To be able to annotate these assembly calls for CFI, they all need
to have a proper C prototype per CPU call.

Define these in a new C file that is only compiled when we use
CFI, and add __ADDRESSABLE() to each so the compiler knows that
these will be addressed (they are not explicitly called in C, they
are called by way of cpu_proc_init() etc).

It is a bit of definitions, but we do not expect new ARM32 CPUs
to appear very much so it should be pretty static.

Tested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>