This is needed before we introduce the fence objects.
Otherwise this will be even more confusing. The plan is to use the following:

seqno: A 32-bit sequence number that may be passed in the fifo.
marker: Objects, carrying a seqno, that track fifo submission time. They
are used for fifo lag based throttling.
fence objects: Kernel space objects, possibly accessible from user-space and
carrying a 32-bit seqno together with signaled status.
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>