Btrfs: trivial sparse fixes

Fix a bunch of trivial sparse complaints.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 1cf4f4f..61af5d8 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -254,7 +254,7 @@
 	wait_for_completion(&fs->kobj_unregister);
 }
 
-int btrfs_init_sysfs()
+int btrfs_init_sysfs(void)
 {
 	btrfs_kset = kset_create_and_add("btrfs", NULL, fs_kobj);
 	if (!btrfs_kset)
@@ -262,7 +262,7 @@
 	return 0;
 }
 
-void btrfs_exit_sysfs()
+void btrfs_exit_sysfs(void)
 {
 	kset_unregister(btrfs_kset);
 }
@@ -289,12 +289,12 @@
 	return;
 }
 
-int btrfs_init_sysfs()
+int btrfs_init_sysfs(void)
 {
 	return 0;
 }
 
-void btrfs_exit_sysfs()
+void btrfs_exit_sysfs(void)
 {
 	return;
 }