i2c: Fix oops on bus multiplexer driver loading

The two I2C bus multiplexer drivers (i2c-amd756-s4882 and
i2c-nforce2-s4985) make use of the bus they want to multiplex before
checking if it is really present. Swap the instructions to test for
presence first. This fixes a oops reported by Ingo Molnar.

Signed-off-by: Jean Delvare <[e-mail]>
Cc: Ingo Molnar <[e-mail]>

drivers/i2c/busses/i2c-amd756-s4882.c

···
 	int i, error;
 	union i2c_smbus_data ioconfig;
 
+	if (!amd756_smbus.dev.parent)
+		return -ENODEV;
+
 	/* Configure the PCA9556 multiplexer */
 	ioconfig.byte = 0x00; /* All I/O to output mode */
 	error = i2c_smbus_xfer(&amd756_smbus, 0x18, 0, I2C_SMBUS_WRITE, 0x03,
···
 	/* Unregister physical bus */
 	error = i2c_del_adapter(&amd756_smbus);
 	if (error) {
-		if (error == -EINVAL)
-			error = -ENODEV;
-		else
-			dev_err(&amd756_smbus.dev, "Physical bus removal "
-				"failed\n");
+		dev_err(&amd756_smbus.dev, "Physical bus removal failed\n");
 		goto ERROR0;
 	}
 

drivers/i2c/busses/i2c-nforce2-s4985.c

···
 	int i, error;
 	union i2c_smbus_data ioconfig;
 
+	if (!nforce2_smbus)
+		return -ENODEV;
+
 	/* Configure the PCA9556 multiplexer */
 	ioconfig.byte = 0x00; /* All I/O to output mode */
 	error = i2c_smbus_xfer(nforce2_smbus, 0x18, 0, I2C_SMBUS_WRITE, 0x03,
···
 	}
 
 	/* Unregister physical bus */
-	if (!nforce2_smbus)
-		return -ENODEV;
 	error = i2c_del_adapter(nforce2_smbus);
 	if (error) {
 		dev_err(&nforce2_smbus->dev, "Physical bus removal failed\n");