w1: w1_therm: use clamp() in int_to_short()

It's slightly cleaner to use the clamp() macro instead of open coding
this.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YEedHNwqEH8fvjkD@mwanda


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>