mfd: Turn on the twl4030-madc MADC clock

Without turning the MADC clock on, no MADC conversions occur.

$ cat /sys/class/hwmon/hwmon0/device/in8_input
[   53.428436] twl4030_madc twl4030_madc: conversion timeout!
cat: read error: Resource temporarily unavailable

Signed-off-by: Kyle Manna <kyle@kylemanna.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

include/linux/i2c/twl4030-madc.h

@@ -129,6 +129,10 @@ enum sample_type {
 #define REG_BCICTL2             0x024
 #define TWL4030_BCI_ITHSENS	0x007
 
+/* Register and bits for GPBR1 register */
+#define TWL4030_REG_GPBR1		0x0c
+#define TWL4030_GPBR1_MADC_HFCLK_EN	(1 << 7)
+
 struct twl4030_madc_user_parms {
 	int channel;
 	int average;