swsusp: fix error paths in snapshot_open

We forget to increase device_available if there's an error in snapshot_open(),
so the snapshot device cannot be open at all after snapshot_open() has
returned an error.
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/power/user.c

@@ -49,12 +49,14 @@ static int snapshot_open(struct inode *inode, struct file *filp)
 	if (!atomic_add_unless(&device_available, -1, 0))
 		return -EBUSY;
 
-	if ((filp->f_flags & O_ACCMODE) == O_RDWR)
+	if ((filp->f_flags & O_ACCMODE) == O_RDWR) {
+		atomic_inc(&device_available);
 		return -ENOSYS;
-
-	if(create_basic_memory_bitmaps())
+	}
+	if(create_basic_memory_bitmaps()) {
+		atomic_inc(&device_available);
 		return -ENOMEM;
-
+	}
 	nonseekable_open(inode, filp);
 	data = &snapshot_state;
 	filp->private_data = data;