hw/pci/aer: Make PCIE AER error injection facility available for other emulation...

hw/pci/aer: Make PCIE AER error injection facility available for other emulation to use.

This infrastructure will be reused for CXL RAS error injection
in patches that follow.

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20230302133709.30373-8-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>