x86/PCI: never allocate PCI MMIO resources below BIOS_END

When we move a PCI device or assign resources to a device not configured
by the BIOS, we want to avoid the BIOS region below 1MB.  Note that if the
BIOS places devices below 1MB, we leave them there.

See https://bugzilla.kernel.org/show_bug.cgi?id=15744
and https://bugzilla.kernel.org/show_bug.cgi?id=15841

Tested-by: Andy Isaacson <adi@hexapodia.org>
Tested-by: Andy Bailey <bailey@akamai.com>
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>