PCI: dwc: all: Split struct pcie_port into host-only and core structures

Keep only the host-specific members in struct pcie_port and move the common
members (i.e common to both host and endpoint) to struct dw_pcie.  This is
in preparation for adding endpoint mode support to designware driver.

While at that also fix checkpatch warnings.

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>