cdx: fix build failure due to sysfs 'bus_type' argument needing to be const

Commit 75cff72 ("driver core: bus: mark the struct bus_type for
sysfs callbacks as constant") missed at least one case - the CDX bus
driver.  Probably because Greg didn't notice the build failure, because
it only ends up being enabled on arm64.

And I missed it during the merge, because while I do arm64 builds these
days, I don't do them in between each pull.  So it took a while for me
to notice the breakage, rather than me just fixing it in the driver core
merge that brought this failure case in.

Maybe we should remove the CDX_BUS dependency on arm64 when COMPILE_TEST
is on?

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Nipun Gupta <nipun.gupta@amd.com>
Cc: Nikhil Agarwal <nikhil.agarwal@amd.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: torvalds

drivers/cdx/cdx.c

@@ -363,7 +363,7 @@ static struct attribute *cdx_dev_attrs[] = {
 };
 ATTRIBUTE_GROUPS(cdx_dev);
 
-static ssize_t rescan_store(struct bus_type *bus,
+static ssize_t rescan_store(const struct bus_type *bus,
 			    const char *buf, size_t count)
 {
 	struct cdx_controller *cdx;