PCI: Initialize RCB from pci_configure_device()

PCI: Initialize RCB from pci_configure_device()

Commit e42010d8207f ("PCI: Set Read Completion Boundary to 128 iff Root
Port supports it (_HPX)") worked around a bogus _HPX type 2 record, which
caused program_hpx_type2() to set the RCB in an endpoint even though the
Root Port did not have the RCB bit set.

e42010d8207f fixed that by setting the RCB in the endpoint only when it was
set in the Root Port.

In retrospect, program_hpx_type2() is intended for AER-related settings,
and the RCB should be configured elsewhere so it doesn't depend on the
presence or contents of an _HPX record.

Explicitly program the RCB from pci_configure_device() so it matches the
Root Port's RCB.  The Root Port may not be visible to virtualized guests;
in that case, leave RCB alone.

Fixes: e42010d8207f ("PCI: Set Read Completion Boundary to 128 iff Root Port supports it (_HPX)")
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20260129175237.727059-2-haakon.bugge@oracle.com