ipmi_si: use smi_num for init_name

Commit 1abf71ee moved the creation of new_smi->dev to earlier in the init
sequence in order to provide infrastructure for log printing.

However, the init_name was created with a hard-coded value of zero. This
presents a problem in systems with more than one interface, producing a
call trace in dmesg.

To correct the problem, simply use smi_num instead of the hard-coded
value of zero.

Tested on a lenovo x3950.

Signed-off-by: Tony Camuso <tcamuso@redhat.com>

There was actually a more general problem, the platform device wasn't
being set correctly, either, and there was a possible (though extremely
unlikely) race on smi_num.  Add locks to clean up the race and use the
proper value for the platform device, too.

Tested on qemu in various configurations.

Signed-off-by: Corey Minyard <cminyard@mvista.com>