regulator: wm831x-ldo: Check return value of wm831x_reg_read()

wm831x_reg_read() returns negative error code on failure.
This prevents using the error code as the value read.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/regulator/wm831x-ldo.c b/drivers/regulator/wm831x-ldo.c
index 5cb70ca..56a6de3 100644
--- a/drivers/regulator/wm831x-ldo.c
+++ b/drivers/regulator/wm831x-ldo.c
@@ -205,6 +205,8 @@
 
 	/* Is it reporting under voltage? */
 	ret = wm831x_reg_read(wm831x, WM831X_LDO_UV_STATUS);
+	if (ret < 0)
+		return ret;
 	if (ret & mask)
 		return REGULATOR_STATUS_ERROR;
 
@@ -469,6 +471,8 @@
 
 	/* Is it reporting under voltage? */
 	ret = wm831x_reg_read(wm831x, WM831X_LDO_UV_STATUS);
+	if (ret < 0)
+		return ret;
 	if (ret & mask)
 		return REGULATOR_STATUS_ERROR;