hwmon: (zl6100) Maintain delay parameter in driver instance data

A global delay parameter has the side effect of being overwritten with 0 if a
single ZL2004 or ZL6105 is instantiated. If other chips supported by the same
driver are in the system, this will result in access errors for those chips.

To solve the problem, keep a per-instance copy of the delay parameter, and do
not change the original parameter.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: stable@vger.kernel.org # 3.1+
Acked-by: Jean Delvare <khali@linux-fr.org>