percpu: remove some sparse warnings

Make the following changes to remove some sparse warnings.

* Make DEFINE_PER_CPU_SECTION() declare __pcpu_unique_* before
  defining it.

* Annotate pcpu_extend_area_map() that it is entered with pcpu_lock
  held, releases it and then reacquires it.

* Make percpu related macros use unique nested variable names.

* While at it, add pcpu prefix to __size_call[_return]() macros as
  to-be-implemented sparse annotations will add percpu specific stuff
  to these macros.

Signed-off-by: Tejun Heo <[email protected]>
Reviewed-by: Christoph Lameter <[email protected]>
Cc: Rusty Russell <[email protected]>

mm/percpu.c

@@ -365,6 +365,7 @@ static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
  * 0 if noop, 1 if successfully extended, -errno on failure.
  */
 static int pcpu_extend_area_map(struct pcpu_chunk *chunk)
+	__releases(lock) __acquires(lock)
 {
 	int new_alloc;
 	int *new;