Windows: Fix HID and synchronous transfer completion

Commit b51c743e42 ("Windows: Filter out non-libusb I/O completions")
causes problems with the HID backend functions and synchronous transfer
completions. Address these by fetching the correct pointer in the HID
functions and posting an I/O completion for synchronous transfers.

Closes #863

Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>
3 files changed