thermal/drivers/tegra: Fix crash when getting critical temp

thermal/drivers/tegra: Fix crash when getting critical temp

Commit 13bea86623be ("thermal/of: Remove of_thermal_get_crit_temp()")
removed the function of_thermal_get_crit_temp() and this is causing a
NULL pointer deference crash when attempting to call the 'get_crit_temp'
function pointer because this function pointer is no longer initialised.
Fix this by replacing the call to the 'get_crit_temp' function pointer
with a call to the function thermal_zone_get_crit_temp() instead.

Fixes: 13bea86623be ("thermal/of: Remove of_thermal_get_crit_temp()")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://lore.kernel.org/r/20221010150311.40384-1-jonathanh@nvidia.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>