ipmi: kcs_bmc_aspeed: Optionally apply status address

Some Aspeed KCS devices can derive the status register address from the
address of the data register. As such, the address of the status
register can be implicit in the configuration if desired. On the other
hand, sometimes address schemes might be requested that are incompatible
with the default addressing scheme. Allow these requests where possible
if the devicetree specifies the status register address.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Chia-Wei Wang <chiawei_wang@aspeedtech.com>
Message-Id: <20210608104757.582199-17-andrew@aj.id.au>
Signed-off-by: Corey Minyard <cminyard@mvista.com>