uio: Fix uio hotplug issues

Protect uio driver from crashing when its owner is unplugged while there are open fds.

Brian Russell (2):
uio: Request/free irq separate from dev lifecycle
uio: Fix uio driver to refcount device

v8: break out irq change into separate patch

v7: use dev_set_name and fix error path in uio_register_device

v6: ... and put them in the right place

v5: add patch version changes

v4: info struct passed in uio_register_device can be freed
on unregister, so null out the field in uio_unregister_device and check accesses.

v3: Embed struct device in struct uio_device, use refcounting on
device, free uio_device on release.

v2: Add blank line to header