Make fdesc_mtx private to kern_descrip.c now that the flock has come home.

sys/kern/kern_descrip.c

@@ -131,7 +131,7 @@ struct sx filelist_lock;	/* sx to protect filelist */
 struct mtx sigio_lock;		/* mtx to protect pointers to sigio */
 
 /* A mutex to protect the association between a proc and filedesc. */
-struct mtx	fdesc_mtx;
+static struct mtx	fdesc_mtx;
 
 /*
  * Find the first zero bit in the given bitmap, starting at low and not

sys/sys/filedesc.h

@@ -182,8 +182,6 @@ fget_locked(struct filedesc *fdp, int fd)
 	return (fd < 0 || fd >= fdp->fd_nfiles ? NULL : fdp->fd_ofiles[fd]);
 }
 
-extern struct mtx fdesc_mtx;
-
 #endif /* _KERNEL */
 
 #endif /* !_SYS_FILEDESC_H_ */