ipmi_si: Fix oops with PCI devices

When the IPMI PCI code was split out, some code was consolidated for
setting the io_setup field in the io structure.  The PCI code needed
this set before registration to probe register spacing, though, so
restore the old code for that function.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=197999
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Tested-by: Meelis Roos <mroos@linux.ee>