mfd: Add device-tree entry to enable tps65910 external 32-kHz oscillator

Add device-tree entry to enable external 32-kHz crystal oscillator
input.

Compile-only tested.
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

Documentation/devicetree/bindings/mfd/tps65910.txt

@@ -29,6 +29,8 @@ Optional properties:
   comparator. (see VMBCH_VSEL in TPS65910 datasheet)
 - ti,vmbch2-threshold: (tps65911) main battery discharged threshold
   comparator. (see VMBCH_VSEL in TPS65910 datasheet)
+- ti,en-ck32k-xtal: enable external 32-kHz crystal oscillator (see CK32K_CTRL
+  in TPS6591X datasheet)
 - ti,en-gpio-sleep: enable sleep control for gpios
   There should be 9 entries here, one for each gpio.
 
@@ -53,7 +55,7 @@ Example:
 
 		ti,vmbch-threshold = 0;
 		ti,vmbch2-threshold = 0;
-
+		ti,en-ck32k-xtal;
 		ti,en-gpio-sleep = <0 0 1 0 0 0 0 0 0>;
 
 		regulators {

drivers/mfd/tps65910.c

@@ -194,6 +194,9 @@ static struct tps65910_board *tps65910_parse_dt(struct i2c_client *client,
 	else if (*chip_id == TPS65911)
 		dev_warn(&client->dev, "VMBCH2-Threshold not specified");
 
+	prop = of_property_read_bool(np, "ti,en-ck32k-xtal");
+	board_info->en_ck32k_xtal = prop;
+
 	board_info->irq = client->irq;
 	board_info->irq_base = -1;