By the original design we assumed that if we "miss" multi CS completion
it is of no severe consequence as we'll just call wait_for_multi_cs
again.

Sequence of events for such scenario:
1. user submit CS with sequence N
2. user calls wait for multi-CS with only CS #N in the list
3. the multi CS call starts with poll of the CSs but find that none
   completed (while CS #N did not completed yet)
4. now, multi CS #N complete but multi CS CTX was not yet created for
   the above multi-CS. so, attempt to complete multi-CS fails (as no
   multi CS CTX exist)
5. wait_for_multi_cs call now does init_wait_multi_cs_completion (and
   for this create the multi-CS CTX)
6. wait_for_multi_cs wits on completion but will not get one as CS #N
   already completed

To fix the issue we initialize the multi-CS CTX prior polling the
fences.
Signed-off-by: Ohad Sharabi <osharabi@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>