x86/PCI: fix bogus host bridge window start/end alignment from _CRS

PCI device BARs are guaranteed to start and end on at least a four-byte
(I/O) or a sixteen-byte (MMIO) boundary because they're aligned on their
size and the low BAR bits are reserved.  PCI-to-PCI bridge apertures
have even larger alignment restrictions.

However, some BIOSes (e.g., HP DL360 BIOS P31) report host bridge windows
like "[io  0x0000-0x2cfe]".  This is wrong because it excludes the last
port at 0x2cff: it's impossible for a downstream device to claim 0x2cfe
without also claiming 0x2cff.  In fact, this BIOS configures a device
behind the bridge to "[io  0x2c00-0x2cff]", so we know the window actually
does include 0x2cff.

This patch rounds the start and end of apertures to the appropriate
boundary.  I experimentally determined that Windows contains a similar
workaround; details here:

    http://bugzilla.kernel.org/show_bug.cgi?id=14337



Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>