hwmon: (lm75) Make the writing to sysfs more robust

Currently we get the checkpatch warning
consider using strict_strtol in preference to simple_strtol.
Also we should not allow any partially numeric values.

Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>