Input: ucb1400 - move static function from header into core

it's a little too large for static line.
The ts is currently the only mainline user but Marek Vasut claims that
there is a battery driver in an ARM tree which also needs this function.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/mfd/ucb1400_core.c b/drivers/mfd/ucb1400_core.c
index 178159e..78c2135 100644
--- a/drivers/mfd/ucb1400_core.c
+++ b/drivers/mfd/ucb1400_core.c
@@ -23,6 +23,26 @@
 #include <linux/module.h>
 #include <linux/ucb1400.h>
 
+unsigned int ucb1400_adc_read(struct snd_ac97 *ac97, u16 adc_channel,
+		int adcsync)
+{
+	unsigned int val;
+
+	if (adcsync)
+		adc_channel |= UCB_ADC_SYNC_ENA;
+
+	ucb1400_reg_write(ac97, UCB_ADC_CR, UCB_ADC_ENA | adc_channel);
+	ucb1400_reg_write(ac97, UCB_ADC_CR, UCB_ADC_ENA | adc_channel |
+			UCB_ADC_START);
+
+	while (!((val = ucb1400_reg_read(ac97, UCB_ADC_DATA))
+				& UCB_ADC_DAT_VALID))
+		schedule_timeout_uninterruptible(1);
+
+	return val & UCB_ADC_DAT_MASK;
+}
+EXPORT_SYMBOL_GPL(ucb1400_adc_read);
+
 static int ucb1400_core_probe(struct device *dev)
 {
 	int err;