ipmi: Don't use BMC product/dev ids in the BMC name

There are a lot of bad things that a set of BMCs could do that
would really confuse the IPMI driver; it's possible for BMCs with
different GUIDs to have the same product/devid (though that's
not technically legal), which would result in platform device
namespace collisions.  Fixing it would involve either using
the GUID in the BMC name, which resulted in huge names, or
just using an ida for numbering the BMCs.  The latter approach
was chosen to avoid the huge names.

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