char: make misc_deregister a void function

With well over 200+ users of this api, there are a mere 12 users that
actually checked the return value of this function.  And all of them
really didn't do anything with that information as the system or module
was shutting down no matter what.

So stop pretending like it matters, and just return void from
misc_deregister().  If something goes wrong in the call, you will get a
WARNING splat in the syslog so you know how to fix up your driver.
Other than that, there's nothing that can go wrong.

Cc: Alasdair Kergon <agk@redhat.com>
Cc: Neil Brown <neilb@suse.com>
Cc: Oleg Drokin <oleg.drokin@intel.com>
Cc: Andreas Dilger <andreas.dilger@intel.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Christine Caulfield <ccaulfie@redhat.com>
Cc: David Teigland <teigland@redhat.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Acked-by: Joel Becker <jlbec@evilplan.org>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index cd7ef34..6bad633 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2163,8 +2163,7 @@
 
 static void btrfs_interface_exit(void)
 {
-	if (misc_deregister(&btrfs_misc) < 0)
-		printk(KERN_INFO "BTRFS: misc_deregister failed for control device\n");
+	misc_deregister(&btrfs_misc);
 }
 
 static void btrfs_print_info(void)
diff --git a/fs/dlm/plock.c b/fs/dlm/plock.c
index e0ab3a9..5532f09 100644
--- a/fs/dlm/plock.c
+++ b/fs/dlm/plock.c
@@ -509,7 +509,6 @@
 
 void dlm_plock_exit(void)
 {
-	if (misc_deregister(&plock_dev_misc) < 0)
-		log_print("dlm_plock_exit: misc_deregister failed");
+	misc_deregister(&plock_dev_misc);
 }
 
diff --git a/fs/dlm/user.c b/fs/dlm/user.c
index fb85f32..75ecc0d 100644
--- a/fs/dlm/user.c
+++ b/fs/dlm/user.c
@@ -362,18 +362,15 @@
 
 int dlm_device_deregister(struct dlm_ls *ls)
 {
-	int error;
-
 	/* The device is not registered.  This happens when the lockspace
 	   was never used from userspace, or when device_create_lockspace()
 	   calls dlm_release_lockspace() after the register fails. */
 	if (!ls->ls_device.name)
 		return 0;
 
-	error = misc_deregister(&ls->ls_device);
-	if (!error)
-		kfree(ls->ls_device.name);
-	return error;
+	misc_deregister(&ls->ls_device);
+	kfree(ls->ls_device.name);
+	return 0;
 }
 
 static int device_user_purge(struct dlm_user_proc *proc,
diff --git a/fs/ocfs2/stack_user.c b/fs/ocfs2/stack_user.c
index 2768eb1..ced70c8 100644
--- a/fs/ocfs2/stack_user.c
+++ b/fs/ocfs2/stack_user.c
@@ -655,14 +655,7 @@
 
 static void ocfs2_control_exit(void)
 {
-	int rc;
-
-	rc = misc_deregister(&ocfs2_control_device);
-	if (rc)
-		printk(KERN_ERR
-		       "ocfs2: Unable to deregister ocfs2_control device "
-		       "(errno %d)\n",
-		       -rc);
+	misc_deregister(&ocfs2_control_device);
 }
 
 static void fsdlm_lock_ast_wrapper(void *astarg)