usb: typec: tcpm/tcpci_maxim: fix error code in max_contaminant_read_resistance_kohm()

If max_contaminant_read_adc_mv() fails, then return the error code.  Don't
return zero.

Fixes: 02b332a ("usb: typec: maxim_contaminant: Implement check_contaminant callback")
Cc: stable <stable@kernel.org>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: André Draszik <andre.draszik@linaro.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/f1bf3768-419e-40dd-989c-f7f455d6c824@stanley.mountain
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Dan Carpenter

drivers/usb/typec/tcpm/maxim_contaminant.c

@@ -135,7 +135,7 @@ static int max_contaminant_read_resistance_kohm(struct max_tcpci_chip *chip,
 
 		mv = max_contaminant_read_adc_mv(chip, channel, sleep_msec, raw, true);
 		if (mv < 0)
-			return ret;
+			return mv;
 
 		/* OVP enable */
 		ret = regmap_update_bits(regmap, TCPC_VENDOR_CC_CTRL2, CCOVPDIS, 0);
@@ -157,7 +157,7 @@ static int max_contaminant_read_resistance_kohm(struct max_tcpci_chip *chip,
 
 	mv = max_contaminant_read_adc_mv(chip, channel, sleep_msec, raw, true);
 	if (mv < 0)
-		return ret;
+		return mv;
 	/* Disable current source */
 	ret = regmap_update_bits(regmap, TCPC_VENDOR_CC_CTRL2, SBURPCTRL, 0);
 	if (ret < 0)