ipmi_si: Load acpi_ipmi when ACPI IPMI interface added

Try to load acpi_ipmi when an ACPI IPMI interface is added, so that the
ACPI IPMI OpRegion is accessible.

Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Message-Id: <20200311192409.59923-1-stuart.w.hayes@gmail.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>