soc: microchip: make mpfs_sys_controller_put static

dsafsdfd0054 ("soc: add microchip polarfire soc system controller")
incorrectly exported mpfs_sys_controller_put. Remove the export and make
the function static instead. This fixes the "no previous prototype
for 'mpfs_sys_controller_put'" warning spotted by the kernel test robot.

Fixes: d0054a470c ("soc: add microchip polarfire soc system controller")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Conor Dooley <mail@conchuod.ie>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/soc/microchip/mpfs-sys-controller.c

@@ -73,13 +73,12 @@ static void mpfs_sys_controller_delete(struct kref *kref)
 	kfree(sys_controller);
 }
 
-void mpfs_sys_controller_put(void *data)
+static void mpfs_sys_controller_put(void *data)
 {
 	struct mpfs_sys_controller *sys_controller = data;
 
 	kref_put(&sys_controller->consumers, mpfs_sys_controller_delete);
 }
-EXPORT_SYMBOL(mpfs_sys_controller_put);
 
 static struct platform_device subdevs[] = {
 	{