w32: Fix access to host devices (regression)

QEMU failed to open host devices like \\.\PhysicalDrive0 (first hard disk)
since some time (commit 8a79380b8ef1b02d2abd705dd026a18863b09020?).

Those devices use hdev_open which did not use the latest API for options.
This resulted in a fatal runtime error:

  Block protocol 'host_device' doesn't support the option 'filename'

Duplicate code from raw_open to fix this.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>