conf: move/rename hostdev PCI driver type enum to device_conf.h

conf: move/rename hostdev PCI driver type enum to device_conf.h

Currently this enum is defined in domain_conf.h and named
virDomainHostdevSubsysPCIDriverType. I want to use it in parts of the
network and networkport config, so am moving its definition to
device_conf.h which is / can be included by all interested parties,
and renaming it to match the name of the corresponding XML attribute
("driver name"). The name change (which includes enum values) does cause a
lot of churn, but it's all mechanical.

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>