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 <[e-mail]>
Tested-by: Andy Bailey <[e-mail]>
Signed-off-by: Bjorn Helgaas <[e-mail]>
Signed-off-by: Jesse Barnes <[e-mail]>

arch/x86/pci/i386.c

···
 			return start;
 		if (start & 0x300)
 			start = (start + 0x3ff) & ~0x3ff;
+	} else if (res->flags & IORESOURCE_MEM) {
+		if (start < BIOS_END)
+			start = BIOS_END;
 	}
 	return start;
 }