ARM/PCI: Move to generic PCI domains

Most if not all ARM PCI host controller device drivers either ignore the
domain field in the pci_sys_data structure or just increment it every time
a host controller is probed, using it as a domain counter.

Therefore, instead of relying on pci_sys_data to stash the domain number in
a standard location, ARM pcibios code can be moved to the newly introduced
generic PCI domains code, implemented in commits:

  41e5c0f8 ("of/pci: Add pci_get_new_domain_nr() and of_get_pci_domain_nr()")
  670ba0c8 ("PCI: Add generic domain handling")

ARM code is made to select PCI_DOMAINS_GENERIC by default, which builds
core PCI code that assigns the domain number through the generic function:

  void pci_bus_assign_domain_nr(...)

that relies on a DT property to define the domain number or falls back to a
counter according to a predefined logic; its usage replaces the current
domain assignment code in PCI host controllers present in the kernel.

Tested-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Yijing Wang <wangyijing@huawei.com>
Reviewed-By: Jason Gunthorpe <jgunthorpe@obsidianresearch.com> # mvebu
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Phil Edworthy <phil.edworthy@renesas.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
CC: Mohit Kumar <mohit.kumar@st.com>