Revert "block: Remove dead deprecation warning code"

Revert "block: Remove dead deprecation warning code"

This reverts commit 6266e900b8083945cb766b45c124fb3c42932cb3.

Some deprecated -drive options were still in use by libvirt, only
fixed with libvirt commit b340c6c614 ("qemu: format serial and geometry
on frontend disk device"), which is not yet in any released version
of libvirt.

So let's hold off removing the deprecated options for one more QEMU
release.

Reported-by: Christian Borntraeger <[email protected]>
Signed-off-by: Cornelia Huck <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>