zorro: Move zorro_bus_type to bus-private header file

zorro_bus_type was never used outside the Zorro bus code.  Hence move it
from the public to the bus-private header file.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20200112164949.20196-6-geert@linux-m68k.org

drivers/zorro/zorro.h

 /* SPDX-License-Identifier: GPL-2.0 */
 
+    /*
+     *  Zorro bus
+     */
+
+extern struct bus_type zorro_bus_type;
+
+
 #ifdef CONFIG_ZORRO_NAMES
 extern void zorro_name_device(struct zorro_dev *z);
 #else

include/linux/zorro.h

@@ -40,13 +40,6 @@ struct zorro_dev {
 #define	to_zorro_dev(n)	container_of(n, struct zorro_dev, dev)
 
 
-    /*
-     *  Zorro bus
-     */
-
-extern struct bus_type zorro_bus_type;
-
-
     /*
      *  Zorro device drivers
      */