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

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: 02b332a06397 ("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>