PCI: Call pci_read_bridge_bases() from core instead of arch code

When we scan a PCI bus, we read PCI-PCI bridge window registers with
pci_read_bridge_bases() so we can validate the resource hierarchy.  Most
architectures call pci_read_bridge_bases() from pcibios_fixup_bus(), but
PCI-PCI bridges are not arch-specific, so this doesn't need to be in
arch-specific code.

Call pci_read_bridge_bases() directly from the PCI core instead of from
arch code.

For alpha and mips, we now call pci_read_bridge_bases() always; previously
we only called it if PCI_PROBE_ONLY was set.

[bhelgaas: changelog]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Ralf Baechle <ralf@linux-mips.org>
CC: James E.J. Bottomley <jejb@parisc-linux.org>
CC: Michael Ellerman <mpe@ellerman.id.au>
CC: Bjorn Helgaas <bhelgaas@google.com>
CC: Richard Henderson <rth@twiddle.net>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: David Howells <dhowells@redhat.com>
CC: Russell King <linux@arm.linux.org.uk>
CC: Tony Luck <tony.luck@intel.com>
CC: David S. Miller <davem@davemloft.net>
CC: Ingo Molnar <mingo@redhat.com>
CC: Guenter Roeck <linux@roeck-us.net>
CC: Michal Simek <monstr@monstr.eu>
CC: Chris Zankel <chris@zankel.net>