cxl/pci: Get AER capability address from RCRB only for RCH dport

cxl/pci: Get AER capability address from RCRB only for RCH dport

cxl_setup_parent_dport() needs to get RCH dport AER capability address
from RCRB to disable AER interrupt. The function does not check if dport
is RCH dport, it will get a wrong pci_host_bridge structure by dport_dev
in VH case because dport_dev points to a pci device(RP or switch DSP)
rather than a pci host bridge device.

Fixes: f05fd10d138d ("cxl/pci: Add RCH downstream port AER register discovery")
Signed-off-by: Li Ming <ming4.li@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Tested-by: Ira Weiny <ira.weiny@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20240809082750.3015641-2-ming4.li@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>