PCI: Update "pci=resource_alignment" documentation

Some uio based PCI drivers, e.g., uio_cif, do not work if the assigned PCI
memory resources are not page aligned.  By using the kernel option
"pci=resource_alignment=<align>@<bus>:<slot>.<func>" it is possible to
request page alignment for memory resources of devices.

However, this is cumbersome when using several devices, and the
bus/slot/func addresses may change if devices are added to or removed from
the system.

Extend the "pci=resource_alignment" option so we can specify the relevant
devices via PCI vendor, device, subvendor, and subdevice IDs.  The
specification of the devices via IDs is indicated by a leading string
"pci:" as argument to "pci=resource_alignment".

The format of the specification is
  pci:<vendor>:<device>[:<subvendor>:<subdevice>]

Examples:
  pci=resource_alignment=4096@pci:8086:9c22:103c:198f
  pci=resource_alignment=pci:8086:9c22       # defaults to PAGE_SIZE align

[bhelgaas: changelog, use actual vendor/device IDs in examples]
Signed-off-by: Mathias Koehrer <mathias.koehrer@etas.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Documentation/kernel-parameters.txt

@@ -3032,6 +3032,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 				PAGE_SIZE is used as alignment.
 				PCI-PCI bridge can be specified, if resource
 				windows need to be expanded.
+				To specify the alignment for several
+				instances of a device, the PCI vendor,
+				device, subvendor, and subdevice may be
+				specified, e.g., 4096@pci:8086:9c22:103c:198f
 		ecrc=		Enable/disable PCIe ECRC (transaction layer
 				end-to-end CRC checking).
 				bios: Use BIOS/firmware settings. This is the