powerpc/sysfs: move to use bus_get_dev_root()

Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.

Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20230313182918.1312597-12-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/powerpc/kernel/sysfs.c

@@ -217,13 +217,18 @@ static DEVICE_ATTR(dscr_default, 0600,
 static void __init sysfs_create_dscr_default(void)
 {
 	if (cpu_has_feature(CPU_FTR_DSCR)) {
+		struct device *dev_root;
 		int cpu;
 
 		dscr_default = spr_default_dscr;
 		for_each_possible_cpu(cpu)
 			paca_ptrs[cpu]->dscr_default = dscr_default;
 
-		device_create_file(cpu_subsys.dev_root, &dev_attr_dscr_default);
+		dev_root = bus_get_dev_root(&cpu_subsys);
+		if (dev_root) {
+			device_create_file(dev_root, &dev_attr_dscr_default);
+			put_device(dev_root);
+		}
 	}
 }
 #endif /* CONFIG_PPC64 */
@@ -746,7 +751,12 @@ static DEVICE_ATTR(svm, 0444, show_svm, NULL);
 
 static void __init create_svm_file(void)
 {
-	device_create_file(cpu_subsys.dev_root, &dev_attr_svm);
+	struct device *dev_root = bus_get_dev_root(&cpu_subsys);
+
+	if (dev_root) {
+		device_create_file(dev_root, &dev_attr_svm);
+		put_device(dev_root);
+	}
 }
 #else
 static void __init create_svm_file(void)