percpu: fix typo in pcpu_setup_first_chunk() comment

s/perpcu/percpu/
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
[Dennis: updated title]

mm/percpu.c

@@ -2220,7 +2220,7 @@ static void pcpu_dump_alloc_info(const char *lvl,
  * @base_addr: mapped address
  *
  * Initialize the first percpu chunk which contains the kernel static
- * perpcu area.  This function is to be called from arch percpu area
+ * percpu area.  This function is to be called from arch percpu area
  * setup path.
  *
  * @ai contains all information necessary to initialize the first