PCI: Widen portdrv service type from 4 bits to 8 bits

PCI: Widen portdrv service type from 4 bits to 8 bits

The names of port service devices previously used one nibble to encode the
port type and another nibble to encode the service type.  We're about to
add a fifth service type, so change device names to use one *byte* to
encode the service type.

For example, a hotplug port service on a downstream bridge was previously
called "pcie24" and is now called "pcie204".  The "2" encodes the device
type (PCI_EXP_TYPE_DOWNSTREAM - 4), and the "4" (now "04") encodes the
service (PCIE_PORT_SERVICE_HP).

Based on Lukas Wunner's patch:
https://github.com/l1k/linux/commit/b688d6e4873ab082e5916b1a993bc1d38c6f4178

[bhelgaas: split to separate patch, expand changelog]
Based-on-patch-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>