rt2x00: Fix BUG on rt2800usb when trying to read eFuse EEPROM.

Current tree hits a BUG_ON in rt2x00_regbusy_read, because the eFuse EEPROM
reading code of rt2800lib uses the function without the csr_mutex locked.

Fix this by locking the csr_mutex for the of the EEPROM reading cycly and
using the _lock variants of the register reading and writing functions.

This also introcudes the register_read_lock function pointer in the
rt2800_ops structure.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt2800lib.h b/drivers/net/wireless/rt2x00/rt2800lib.h
index 7c79011..535ce22 100644
--- a/drivers/net/wireless/rt2x00/rt2800lib.h
+++ b/drivers/net/wireless/rt2x00/rt2800lib.h
@@ -23,6 +23,8 @@
 struct rt2800_ops {
 	void (*register_read)(struct rt2x00_dev *rt2x00dev,
 			      const unsigned int offset, u32 *value);
+	void (*register_read_lock)(struct rt2x00_dev *rt2x00dev,
+				   const unsigned int offset, u32 *value);
 	void (*register_write)(struct rt2x00_dev *rt2x00dev,
 			       const unsigned int offset, u32 value);
 	void (*register_write_lock)(struct rt2x00_dev *rt2x00dev,
@@ -49,6 +51,15 @@
 	rt2800ops->register_read(rt2x00dev, offset, value);
 }
 
+static inline void rt2800_register_read_lock(struct rt2x00_dev *rt2x00dev,
+					     const unsigned int offset,
+					     u32 *value)
+{
+	const struct rt2800_ops *rt2800ops = rt2x00dev->priv;
+
+	rt2800ops->register_read_lock(rt2x00dev, offset, value);
+}
+
 static inline void rt2800_register_write(struct rt2x00_dev *rt2x00dev,
 					 const unsigned int offset,
 					 u32 value)