SENSORS_LIMIT and clamp_val have the same functionality, so retire SENSORS_LIMIT
as it is no longer needed.

The change reduces text size by 26 bytes and bss size by 16 bytes on x86_86
builds.
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Acked-by: NJean Delvare <khali@linux-fr.org>