i2c: Convert the pca9539 driver to a new-style i2c driver

The new-style pca9539 driver implements the optional detect() callback
to cover the use cases of the legacy driver.

Warning: users will now have to use the force module parameter to get
the driver to attach to their device. That's not a bad thing as these
devices can't be detected anyway.

Note that this doesn't change the fact that this driver is deprecated
in favor of gpio/pca953x.

Signed-off-by: Jean Delvare <khali@linux-fr.org>

Documentation/i2c/chips/pca9539

@@ -7,7 +7,7 @@ drivers/gpio/pca9539.c instead.
 Supported chips:
   * Philips PCA9539
     Prefix: 'pca9539'
-    Addresses scanned: 0x74 - 0x77
+    Addresses scanned: none
     Datasheet:
         http://www.semiconductors.philips.com/acrobat/datasheets/PCA9539_2.pdf
 
@@ -23,6 +23,14 @@ The input sense can also be inverted.
 The 16 lines are split between two bytes.
 
 
+Detection
+---------
+
+The PCA9539 is difficult to detect and not commonly found in PC machines,
+so you have to pass the I2C bus and address of the installed PCA9539
+devices explicitly to the driver at load time via the force=... parameter.
+
+
 Sysfs entries
 -------------