regulator: anatop: patching to device-tree property "reg".

Change "reg" to "anatop-reg-offset" due to there is a warning of handling no
size field in reg.

This patch also adds the missing device-tree binding documentation.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/regulator/anatop-regulator.c b/drivers/regulator/anatop-regulator.c
index 17499a5..53969af 100644
--- a/drivers/regulator/anatop-regulator.c
+++ b/drivers/regulator/anatop-regulator.c
@@ -138,9 +138,10 @@
 	rdesc->type = REGULATOR_VOLTAGE;
 	rdesc->owner = THIS_MODULE;
 	sreg->mfd = anatopmfd;
-	ret = of_property_read_u32(np, "reg", &sreg->control_reg);
+	ret = of_property_read_u32(np, "anatop-reg-offset",
+				   &sreg->control_reg);
 	if (ret) {
-		dev_err(dev, "no reg property set\n");
+		dev_err(dev, "no anatop-reg-offset property set\n");
 		goto anatop_probe_end;
 	}
 	ret = of_property_read_u32(np, "anatop-vol-bit-width",