module: encapsulate percpu handling better and record percpu_size

Better encapsulate module static percpu area handling so that code
outsidef of CONFIG_SMP ifdef doesn't deal with mod->percpu directly
and add mod->percpu_size and record percpu_size in it.  Both percpu
fields are compiled out on UP.  While at it, mark mod->percpu w/
__percpu.

This is to prepare for is_module_percpu_address().

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>

include/linux/module.h

@@ -330,8 +330,11 @@ struct module
 	struct module_notes_attrs *notes_attrs;
 #endif
 
+#ifdef CONFIG_SMP
 	/* Per-cpu data. */
-	void *percpu;
+	void __percpu *percpu;
+	unsigned int percpu_size;
+#endif
 
 	/* The command line arguments (may be mangled).  People like
 	   keeping pointers to this stuff */