ARM/PCI: Remove pci_fixup_irqs() call for bios32 host controllers

Legacy PCI host controllers (ie host controllers that set-up the PCI bus
through the ARM pci_common_init() API) are currently relying on
pci_fixup_irqs() to assign legacy PCI irqs to devices.  This is not ideal
in that pci_fixup_irqs() assigns IRQs for all PCI devices present in a given
system some of which may well be enabled by the time pci_fixup_irqs() is
called (ie a system with multiple host controllers).  With the introduction
of struct pci_host_bridge.(*map_irq) pointer it is possible to assign IRQs
for all devices originating from a PCI host bridge at probe time; this is
implemented through pci_assign_irq() that relies on the struct
pci_host_bridge.map_irq pointer to map IRQ for a given device.

The benefits this brings are twofold:

  - the IRQ for a device is assigned once at probe time
  - the IRQ assignment works also for hotplugged devices

Remove pci_fixup_irqs() call from bios32 code and rely on pci_assign_irq()
to carry out the IRQ mapping at device probe time.

The map_irq() and swizzle_irq() struct pci_host_bridge callbacks are set-up
in the struct pci_host_bridge created in the bios32 pcibios_init_hw()
function and mach-* code paths (for PCI mach implementations that require a
specific struct hw_pci.(*scan) function callback).

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
[bhelgaas: folded in fixes from Lorenzo:
http://lkml.kernel.org/r/20170701140629.GC8977@red-moon

]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Andrew Lunn <andrew@lunn.ch>