PCI: dwc: all: Use platform_set_drvdata() to save private data

Add platform_set_drvdata() in all designware-based drivers to store the
private data structure of the driver so that dev_set_drvdata() can be used
to get back private data structure in add_pcie_port/host_init.  This is in
preparation for splitting struct pcie_port into core and host only
structures. After the split pcie_port will not be part of the driver's
private data structure and *container_of* used now to get the private data
pointer cannot be used.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Jingoo Han <jingoohan1@gmail.com>
CC: Richard Zhu <hongxing.zhu@nxp.com>
CC: Lucas Stach <l.stach@pengutronix.de>
CC: Murali Karicheri <m-karicheri2@ti.com>
CC: Minghuan Lian <minghuan.Lian@freescale.com>
CC: Mingkai Hu <mingkai.hu@freescale.com>
CC: Roy Zang <tie-fei.zang@freescale.com>
CC: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
CC: Niklas Cassel <niklas.cassel@axis.com>
CC: Jesper Nilsson <jesper.nilsson@axis.com>
CC: Joao Pinto <Joao.Pinto@synopsys.com>
CC: Zhou Wang <wangzhou1@hisilicon.com>
CC: Gabriele Paoloni <gabriele.paoloni@huawei.com>
CC: Stanimir Varbanov <svarbanov@mm-sol.com>
CC: Pratyush Anand <pratyush.anand@gmail.com>