char:ipmi: Fix a not-used variable on a non-ACPI system

Put some code into APCI ifdefs to avoid a not-used variable warning.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202412222349.R7qW7Q2t-lkp@intel.com/


Signed-off-by: Corey Minyard <corey@minyard.net>