uml: port mutex conversion

The port_sem is already used as a mutex since it's using DECLARE_MUTEX(), but
the underlying construct is still a semaphore .. This patch switches it over
to a struct mutex.

Signed-off-by: Daniel Walker <[e-mail]>
Signed-off-by: Jeff Dike <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/um/drivers/port_kern.c

···
 #include "linux/completion.h"
 #include "linux/interrupt.h"
 #include "linux/list.h"
+#include "linux/mutex.h"
 #include "asm/atomic.h"
 #include "init.h"
 #include "irq_kern.h"
···
 	return 0;
 }
 
-static DECLARE_MUTEX(ports_sem);
+static DEFINE_MUTEX(ports_mutex);
 static LIST_HEAD(ports);
 
 static void port_work_proc(struct work_struct *unused)
···
 	struct port_dev *dev = NULL;
 	int fd;
 
-	down(&ports_sem);
+	mutex_lock(&ports_mutex);
 	list_for_each(ele, &ports) {
 		port = list_entry(ele, struct port_list, list);
 		if (port->port == port_num)
···
  out_free:
 	kfree(port);
  out:
-	up(&ports_sem);
+	mutex_unlock(&ports_mutex);
 	return dev;
 }