With SPD5118 chip detection for the most part handled by the i2c-smbus
core using DMI information, the spd5118 driver no longer needs to
auto-detect spd5118 compliant chips.

Auto-detection by the driver is still needed on systems with no DMI support
or on systems with more than eight DIMMs and can not be removed entirely.
However, it affects boot time and introduces the risk of mis-identifying
chips. Add configuration option to be able to disable it on systems where
chip detection is handled outside the driver.

Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Tested-by: Armin Wolf <W_Armin@gmx.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>