PCI: Move DesignWare IP support to new drivers/pci/dwc/ directory

Group all the PCI drivers that use DesignWare core in dwc directory.
dwc IP is capable of operating in both host mode and device mode and
keeping it inside the *host* directory is misleading.

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