Core: Cache device descriptors in the core
Discussion: It is necessary to cache the device descriptor in the core to
support reading the descriptors after a device is disconnected. We could
either 1) allow each backend to handle this caching (which would most
certainly duplicate code), or 2) cache the descritors when a device
is added. This patch does the later.
Further discussion: It might be beneficial to cache more than just the
device descriptors in the core. It might also be worthwhile caching the
configuration and BOS descriptors as well.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>