hwmon: (ltc2945) Handle error case in ltc2945_value_store

ltc2945_val_to_reg errors were not being handled
which would have resulted in register being set to
0 (clamped) instead of being left alone.

Fixes: 6700ce03 ("hwmon: Driver for Linear Technologies LTC2945")
Signed-off-by: Jonathan Cormier <jcormier@criticallink.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/ltc2945.c

@@ -254,6 +254,8 @@ static ssize_t ltc2945_value_store(struct device *dev,
 
 	/* convert to register value, then clamp and write result */
 	regval = ltc2945_val_to_reg(dev, reg, val);
+	if (regval < 0)
+		return regval;
 	if (is_power_reg(reg)) {
 		regval = clamp_val(regval, 0, 0xffffff);
 		regbuf[0] = regval >> 16;