PCI: designware: Make driver arch-agnostic

Previously, dw_pcie_host_init() created the PCI host bridge with
pci_common_init_dev(), an ARM-specific function that supplies the ARM-
specific pci_sys_data structure as the PCI "sysdata".

Make pcie-designware.c arch-agnostic by reimplementing the functionality of
pci_common_init_dev() directly in dw_pcie_host_init().

Note that this changes the bridge sysdata from the ARM pci_sys_data to the
DesignWare pcie_port structure.  This doesn't affect the ARM sysdata users
because they are all specific to non-DesignWare host bridges, which will
still have pci_sys_data.

[bhelgaas: changelog]
Tested-by: James Morse <james.morse@arm.com>
Tested-by: Gabriel Fernandez <gabriel.fernandez@st.com>
Tested-by: Minghuan Lian <Minghuan.Lian@freescale.com>
Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
Signed-off-by: Gabriele Paoloni <gabriele.paoloni@huawei.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Pratyush Anand <pratyush.anand@gmail.com>