hwmon: (lm78) Fix overflow problems seen when writing large temperature limits

commit 1074d683a51f1aded3562add9ef313e75d557327 upstream.

On platforms with sizeof(int) < sizeof(long), writing a temperature
limit larger than MAXINT will result in unpredictable limit values
written to the chip. Avoid auto-conversion from long to int to fix
the problem.

Cc: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>