misc: pci_endpoint_test: Add the layerscape EP device support

Add the layerscape EP device support in pci_endpoint_test driver.

Signed-off-by: Xiaowei Bao <xiaowei.bao@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Minghuan Lian <minghuan.lian@nxp.com>
Reviewed-by: Zhiqiang Hou <zhiqiang.hou@nxp.com>
Reviewed-by: Greg KH <gregkh@linuxfoundation.org>