maple: make maple_bus_type static and const

There is no need to export maple_bus_type as no one uses it outside of
maple.c, so make it static, AND make it const as it can be read-only as
no one modifies it.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: <linux-sh@vger.kernel.org>
Link: https://lore.kernel.org/r/2023121918-rejoicing-frostlike-d976@gregkhSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/sh/maple/maple.c

@@ -59,6 +59,7 @@ struct maple_device_specify {
 static bool checked[MAPLE_PORTS];
 static bool empty[MAPLE_PORTS];
 static struct maple_device *baseunits[MAPLE_PORTS];
+static const struct bus_type maple_bus_type;
 
 /**
  * maple_driver_register - register a maple driver
@@ -773,11 +774,10 @@ static struct maple_driver maple_unsupported_device = {
 /*
  * maple_bus_type - core maple bus structure
  */
-struct bus_type maple_bus_type = {
+static const struct bus_type maple_bus_type = {
 	.name = "maple",
 	.match = maple_match_bus_driver,
 };
-EXPORT_SYMBOL_GPL(maple_bus_type);
 
 static struct device maple_bus = {
 	.init_name = "maple",

include/linux/maple.h

@@ -5,7 +5,6 @@
 #include <mach/maple.h>
 
 struct device;
-extern struct bus_type maple_bus_type;
 
 /* Maple Bus command and response codes */
 enum maple_code {