ARM: riscpc: make ecard_bus_type constant

Since commit d492cc2 ("driver core: device.h: make struct
bus_type a const *"), the driver core can properly handle constant
struct bus_type, move the ecard_bus_type variable to be a constant
structure as well, placing it into read-only memory which can not be
modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240823081444.150976-1-kunwu.chan@linux.dev
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: KunWuChan

arch/arm/include/asm/ecard.h

@@ -195,7 +195,7 @@ void __iomem *ecardm_iomap(struct expansion_card *ec, unsigned int res,
 			   unsigned long offset, unsigned long maxsize);
 #define ecardm_iounmap(__ec, __addr)	devm_iounmap(&(__ec)->dev, __addr)
 
-extern struct bus_type ecard_bus_type;
+extern const struct bus_type ecard_bus_type;
 
 #define ECARD_DEV(_d)	container_of((_d), struct expansion_card, dev)
 

arch/arm/mach-rpc/ecard.c

@@ -1124,7 +1124,7 @@ static int ecard_match(struct device *_dev, const struct device_driver *_drv)
 	return ret;
 }
 
-struct bus_type ecard_bus_type = {
+const struct bus_type ecard_bus_type = {
 	.name		= "ecard",
 	.dev_groups	= ecard_dev_groups,
 	.match		= ecard_match,