ipmi: kcs: Fix aspeed_kcs_probe_of_v1()

This needs to return the newly allocated struct but instead it returns
zero which leads to an immediate Oops in the caller.

Fixes: 09f5f680

 ("ipmi: kcs: aspeed: Implement v2 bindings")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Message-Id: <20200407122149.GA100026@mwanda>
Signed-off-by: Corey Minyard <cminyard@mvista.com>