ipmi: docs: don't advertise deprecated sysfs entries

"i2c-adapter" class entries are deprecated since 2009. Switch to the
proper location.

Reported-by: Heiner Kallweit <hkallweit1@gmail.com>
Closes: https://lore.kernel.org/r/80c4a898-5867-4162-ac85-bdf7c7c68746@gmail.com


Fixes: 25930707 ("ipmi: Add SMBus interface driver (SSIF)")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Message-Id: <20240901090211.3797-2-wsa+renesas@sang-engineering.com>
Signed-off-by: Corey Minyard <corey@minyard.net>