[coreboot] IPMI driver in romstage

Hi everyone,
In the current implementation, IPMI driver is initialized and ready for use in ramstage, but there are some scenarios that would be better to have IPMI
ready earlier in romstage. For example, setting and starting a BMC watchdog timer via IPMI in romstage, or adding a SEL record right after memory is ready., etc.
Appreciate your thoughts on this, please advice.

Thanks.