mfd: Copy the device pointer to the twl4030-madc structure

Worst case this fixes the following error:
[   72.086212] (NULL device *): conversion timeout!

Best case it prevents a crash
Signed-off-by: Kyle Manna <kyle@kylemanna.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/twl4030-madc.c

@@ -706,6 +706,8 @@ static int __devinit twl4030_madc_probe(struct platform_device *pdev)
 	if (!madc)
 		return -ENOMEM;
 
+	madc->dev = &pdev->dev;
+
 	/*
 	 * Phoenix provides 2 interrupt lines. The first one is connected to
 	 * the OMAP. The other one can be connected to the other processor such