PHYLIB: Locking fixes for PHY I/O potentially sleeping

PHY read/write functions can potentially sleep (e.g., a PHY accessed
via I2C).  The following changes were made to account for this:

    * Change spin locks to mutex locks
    * Add a BUG_ON() to phy_read() phy_write() to warn against
      calling them from an interrupt context.
    * Use work queue for PHY state machine handling since
      it can potentially sleep
    * Change phydev lock from spinlock to mutex

Signed-off-by: Nate Case <ncase@xes-inc.com>
Acked-by: Andy Fleming <afleming@freescale.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index c30196d..6e9f619 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -49,7 +49,7 @@
 	int i;
 	int err = 0;
 
-	spin_lock_init(&bus->mdio_lock);
+	mutex_init(&bus->mdio_lock);
 
 	if (NULL == bus || NULL == bus->name ||
 			NULL == bus->read ||