fix:mailbox:bcm-pdc-mailbox:mark symbols static where possible

We get 2 warnings when biuld kernel with W=1:
drivers/mailbox/bcm-pdc-mailbox.c:472:6: warning: no previous prototype for 'pdc_setup_debugfs' [-Wmissing-prototypes]
drivers/mailbox/bcm-pdc-mailbox.c:488:6: warning: no previous prototype for 'pdc_free_debugfs' [-Wmissing-prototypes]

In fact, these functions are only used in the file in which they are
declared and don't need a declaration, but can be made static.
so this patch marks these functions with 'static'.
Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/bcm-pdc-mailbox.c

@@ -469,7 +469,7 @@ static const struct file_operations pdc_debugfs_stats = {
  * this directory for a SPU.
  * @pdcs: PDC state structure
  */
-void pdc_setup_debugfs(struct pdc_state *pdcs)
+static void pdc_setup_debugfs(struct pdc_state *pdcs)
 {
 	char spu_stats_name[16];
 
@@ -485,7 +485,7 @@ void pdc_setup_debugfs(struct pdc_state *pdcs)
 						  &pdc_debugfs_stats);
 }
 
-void pdc_free_debugfs(void)
+static void pdc_free_debugfs(void)
 {
 	if (debugfs_dir && simple_empty(debugfs_dir)) {
 		debugfs_remove_recursive(debugfs_dir);