arm64: defconfig: Enable some IPMI configs

The arm64 port now runs on servers which use IPMI. This patch enables
relevant core configs to save manually enabling them when testing
mainline.

Signed-off-by: John Garry <john.garry@huawei.com>
[olof: Switched to =m instead of =y]
Signed-off-by: Olof Johansson <olof@lixom.net>