thermal: ti-soc-thermal: Fix reversed condition in ti_thermal_expose_sensor()

This condition is reversed and will cause breakage.

Fixes: 7440f518

 ("thermal/drivers/ti-soc-thermal: Avoid dereferencing ERR_PTR")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200616091949.GA11940@mwanda