thermal: intel: int340x: Drop pointless cast to unsigned long

The explicit casting from int to unsigned long in
int340x_thermal_get_zone_temp() is pointless, becuase the multiplication
result is cast back to int by the assignment in the same statement, so
drop it.

No expected functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Zhang Rui <rui.zhang@intel.com>