hwmon: (ntc_thermistor) Ensure that data->name string is terminated

Fix Coverity warning: Calling strncpy with a maximum size argument of 20 bytes
on destination array "data->name" of size 20 bytes might leave the destination
string unterminated.

Fix by replacing strncpy() with strlcpy() and by using sizeof() to determine
the maximum string length.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Jean Delvare <khali@linux-fr.org>