hw/ipmi/ipmi_bmc_sim: Support getting fake LAN channel config

hw/ipmi/ipmi_bmc_sim: Support getting fake LAN channel config

The following IPMI commands are added or modified to support getting
fake LAN channel configurations from the `ipmi_bmc_sim` device:
* Get Channel Access;
* Get Channel Info Command;
* Get LAN Configuration Parameters.

The fake LAN channel configurations can be specified from QEMU
commandline options for device `ipmi_bmc_sim`. Inside the guest OS, the
configurations can be retrieved from the device using some IPMI tools,
e.g., `ipmitool lan print`.
Note, there is not a real LAN channel. The fake LAN channel is suitable
for testing purposes.

Signed-off-by: Yunpeng Yang <yunpeng.yang@nutanix.com>
Message-ID: <20260105155648.1037077-2-yunpeng.yang@nutanix.com>
Signed-off-by: Corey Minyard <corey@minyard.net>