binfmt_misc: add missing 'break' statement

A missing 'break' statement in bm_status_write() results in a user program
receiving '3' when doing the following:

  write(fd, "-1", 2);
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/binfmt_misc.c

@@ -656,6 +656,7 @@ static ssize_t bm_status_write(struct file * file, const char __user * buffer,
 
 			mutex_unlock(&root->d_inode->i_mutex);
 			dput(root);
+			break;
 		default: return res;
 	}
 	return count;